Redefining Knowledge and Expanding the Moral Circle: The Principle of the Intensity of Existence in Transcendent Theosophy as a Critique of Peter Singer’s Environmental Ethical Theory

1. Introduction

Contemporary environmental ethics faces a fundamental challenge: on what basis can moral value be attributed to inanimate nature without either reducing it to anthropomorphism or leading to a form of pseudo-psychism? This problem becomes particularly acute and academically demanding when engaging with the ethical theory of Peter Singer, the most prominent contemporary consequentialist philosopher. Singer, within the framework of preference utilitarianism, argues that the sphere of morality should be expanded based on the criteria of sentience and conscious preferences. From this perspective, beings lacking a nervous system not only have no preferences but also cannot, in principle, become direct subjects of moral value. Singer (1993, p. 112) explicitly states that if we cannot demonstrate that a being is aware of its own state, we have no basis for attributing any preference to it. This position clearly includes plants, inanimate objects, and ecosystems, which can only be protected indirectly through the interests of humans or sentient animals (Singer, 1975, p. 215). However, the question this study raises is whether this limitation of Singer’s theory stems from preference utilitarianism itself, or from a specific epistemological presupposition that Singer implicitly accepts. The main hypothesis of this study is that the aforementioned limitation arises not from the principle of consequentialism but from Singer’s specific definition of knowledge as a mental and propositional state. In other words, what restricts Singer’s moral circle to sentient beings is not the instrument of utilitarianism but his conception of consciousness and knowledge. To substantiate this hypothesis, the study proceeds in three argumentative steps: First, Singer’s epistemological presupposition is systematically reconstructed and analyzed. Second, an alternative redefinition of knowledge is proposed based on Mulla Sadra’s Transcendent Theosophy. Third, it is demonstrated that this redefinition, without altering the structure of preference utilitarianism, extends the moral circle to all levels of existence.

In contrast, this study argues that the redefinition of knowledge as a mode of existence in Mulla Sadra’s Transcendent Theosophy provides an epistemological basis for extending the moral circle to all levels of existence, without resulting in pseudo-psychism or reducing ontological differences. The specific achievement of this study is the formulation of the principle of the intensity of existence as a criterion for moral value. This principle can be formulated as follows: the moral value of a being is directly proportional to the degree of intensity of existence possessed by that being, and the intensity of existence is identical to the degree of its existential consciousness. From this principle, it follows that a continuum of moral value flows from the weakest level in inanimate objects to the strongest level in human beings, and that there is no discrete gap between beings with a nervous system and those without.

The discussion regarding the scope of the moral circle and the criteria for including beings within it has a long-standing history in Western philosophy. From Aristotle, who regarded logos as the criterion for dignity, to Kant, who posited practical reason as the condition for membership in the kingdom of ends, a boundary has always been drawn between beings inside and outside the circle. By advancing the theory of the expanding moral circle, Singer took an important step toward transcending anthropocentrism (Singer, 2011, p. 45). However, his criterion of sentience, while including animals, excludes inanimate nature. Some critics have shown that Singer's reliance on empirical foundations for defining consciousness entails the acceptance of specific philosophical presuppositions that themselves require justification. Nevertheless, the discussion of the underlying epistemological presupposition of Singer's theory has received less attention.

 In Transcendent Theosophy, the problem of knowledge and consciousness is formulated not within the framework of empirical psychology but within an ontological horizon. Criticizing the Peripatetic definition of knowledge as the impression of the form of an object in the mind, Mulla Sadra establishes the theory of the union of the knower and the known, according to which knowledge is a mode of existence, and its levels are identical to the levels of existence (Mulla Sadra, 2002, vol. 3, p. 280). More precisely, Mulla Sadra argues that if knowledge were merely the impression of a form in the mind, there would be no guarantee that the form corresponds to external reality. Therefore, knowledge must be the very presence of the disclosed object before the knower (Mulla Sadra, 2002, vol. 3, p. 290). This redefinition transforms knowledge from a psychological matter into an ontological one. The principle of the gradation of existence further completes this point: existence possesses degrees of intensity and weakness, and each degree of existence is accompanied by a degree of knowledge and consciousness (Mulla Sadra, 2002, vol. 1, p. 135). Therefore, consciousness in Transcendent Theosophy is not a discrete or binary phenomenon but a continuous spectrum extending from the weakest degree in inanimate objects to the strongest degree in human beings or beyond.

So far, good works has been done in Iran on Mulla Sadra and environmental ethics, but no comparative study has yet been conducted between Mulla Sadra and Singer—who is himself one of the prominent thinkers in the field of environmental ethics. This in itself constitutes one of the novelties of the present research. The method of this study is philosophical-analytical with a critical-comparative approach. This method proceeds in four steps. The first step is the reconstructive argumentation of Singer's theory, during which the epistemological foundations of Singer's environmental ethical theory are systematically reconstructed and its hidden presuppositions are extracted. In this step, it is demonstrated that Singer's definition of consciousness is not an empirical discovery but a philosophical choice that requires justification. The second step is the explication of the Sadraean redefinition, in which the theory of knowledge in Transcendent Theosophy is analyzed with a focus on the concepts of the principality of existence, the gradation of existence, and the union of the knower and the known. In this step, emphasis is placed on the internal arguments of this theory. The third step is the critical comparison, in which the two epistemological frameworks are assessed in relation to each other, and the central question is whether the Sadraean redefinition can resolve the limitation of Singer's theory while preserving the structure of preference utilitarianism. In this step, it is shown that Singer cannot simply reject the Sadraean redefinition, as he himself is compelled to accept certain philosophical presuppositions. The fourth step is the formulation of the achievement, in which the principle of the intensity of existence as a criterion for moral value is ultimately presented and justified as the study's achievement. An important methodological note is that the study is not a mere description of the thoughts of Singer or Mulla Sadra, but rather an argumentative analysis of the relationship between their epistemological foundations and the ethical implications of these foundations.

2. Singer's Theory and Identifying His Epistemological Presupposition

To critique the epistemological foundation of Peter Singer's environmental ethical theory, the theory must first be reconstructed in a systematic and step-by-step manner. Systematic reconstruction means identifying the constituent components of the theory, discovering the logical relationships among them, and finally extracting the presuppositions upon which the theory rests but which Singer himself has not independently justified. This work, without being reduced to mere description, provides the basis for the subsequent critique.

Singer's ethical theory is formulated within the framework of preference utilitarianism. Preference utilitarianism is one of the main branches of consequentialist moral philosophy which, unlike classical Benthamite and Millian utilitarianism that took pleasure and pain as the basis of valuation, considers the conscious preferences of beings as the criterion for the rightness or wrongness of actions. Singer (1993, p. 12) explains this theory by writing that an action is morally right if and only if the consequences of that action satisfy the preferences of all affected beings to the greatest possible extent. This definition distinguishes preference utilitarianism from other versions of utilitarianism in two respects. The first respect is that the criterion of value is not objective pleasure but the subjective and conscious preferences of beings. The second respect is that the circle of beings possessing preferences is not limited to human beings; rather, any being that can have a preference is included in moral calculations.

But the fundamental question is: which beings possess preferences? Or more precisely, what is the necessary and sufficient condition for attributing a preference to a being? Singer's answer to this question is presented on two levels. On the first level, he proposes the criterion of sentience. Sentience means the capacity to experience pleasure and pain, or more generally, the capacity to have conscious states. Singer (1993, p. 95) specifies that the boundary of the moral circle is determined based on the capacity to feel. From this perspective, any being that can experience pain has a preference to avoid that pain. Any being that can experience pleasure has a preference to obtain that pleasure. This approach allows Singer to extend the moral circle from humans to sentient animals. Singer (1975, p. 7) argues in Animal Liberation that many non-human animals, especially mammals and birds, are undoubtedly capable of experiencing pain and pleasure and therefore must be included within the moral circle.

However, the second level of Singer's answer is more precise and more decisive for the present discussion. Singer (1993, p. 112) elsewhere articulates the condition of consciousness more explicitly: a being possesses a preference only if it can be shown that it is aware of its own state. This condition makes consciousness a necessary condition for having a preference. In other words, the mere capacity to respond to stimuli or to have goal-directed behaviors is not sufficient for attributing a preference. What is necessary is the existence of an inner, mental life in which the being can consciously experience its own state. Singer (2011, p. 45) develops this point in The Expanding Circle within the framework of evolutionary theory and evolutionary psychology. He argues that consciousness is an evolutionary phenomenon that emerged along the development of the nervous system. The more complex the nervous system, the greater the capacity for consciousness.

Now we reach the core of the discussion. Singer needs an operational criterion to be able to practically determine which beings possess consciousness. What is this operational criterion? Singer (1993, p. 95) answers that the presence of a nervous system, and especially the presence of structures that in humans are associated with consciousness, is the best empirical indicator of consciousness. He specifies that although we cannot directly prove animal consciousness, neuro-anatomical and behavioral similarities allow us to reasonably conclude that animals with similar nervous systems have consciousness. Conversely, beings that lack any nervous system have no empirical indicator of consciousness and therefore cannot be attributed consciousness. This includes plants, fungi, unicellular organisms, and inanimate objects. Singer's definition of consciousness can be formulated as follows: consciousness is the capacity to process information through a nervous system such that this processing is accompanied by an inner mental life. This definition has three main components. The first component ties consciousness to a physical substrate, namely the nervous system. The second component makes consciousness dependent on information processing. The third component accompanies consciousness with the existence of an inner mental life that is not reducible to information processing. These three components together yield a definition that is apparently both empirically investigable and consistent with common intuitions about consciousness. But is this definition truly an empirical discovery or a philosophical choice? To answer this question, the structure of Singer's argument must be reconstructed step by step and the hidden presuppositions of each step revealed. This reconstruction is carried out in seven steps.

Step one: Singer believes that only beings that possess consciousness have preferences. This step is accepted as a normative principle within preference utilitarianism. However, this principle itself requires justification. Why should unconscious preferences not be included in moral calculations? Singer (1993, p. 114) justifies this principle by noting that preferences without consciousness lack any moral significance because a being that is not aware of its own state cannot suffer from the violation of its preference. This argument introduces consciousness as a condition for the possibility of suffering and consequently as a condition for the moral significance of preferences.

Step two: Singer defines consciousness as the capacity to experience mental states such as pleasure and pain. This definition equates consciousness with sentience. Singer (1993, p. 95) writes that the boundary of the moral circle is determined based on the capacity to feel. This step is also a conceptual choice. Consciousness could be defined otherwise. For example, consciousness could be defined simply as the existence of an internal perspective or, in Thomas Nagel's phrase, there being something it is like to be that being. Such a definition is not necessarily reducible to sentience.

Step three: For the practical identification of beings possessing consciousness, Singer relies on the presence of a nervous system as an empirical indicator. He states that the best evidence for the existence of consciousness in a being is the presence of neural structures like those associated with consciousness in humans (Singer, 1993, p. 98). This step introduces a methodological rule: inferring similarity of consciousness from neuro-anatomical similarity. This rule is based on the presupposition that consciousness is an exclusively physical phenomenon dependent on specific neural substrates.

Step four: Applying this rule, Singer concludes that animals with complex nervous systems possess consciousness. He also concludes that beings lacking a nervous system, such as plants and inanimate objects, cannot have consciousness (Singer, 1993, p. 112). This conclusion follows directly from the methodological rule of step three.

Step five: Since plants and inanimate objects lack consciousness, they cannot have preferences. This step is the logical consequence of combining step one and step four.

Step six: Since plants and inanimate objects do not have preferences, they are not included in the moral calculations of preference utilitarianism. They cannot be made the direct subjects of moral obligations.

Step seven: The only way to protect plants and inanimate objects is through their indirect interests for humans or sentient animals. Singer (1975, p. 215) specifies that if the destruction of a forest causes suffering to the animals living in it, then that destruction is morally wrong. However, if the same forest lacks any animal life, there is no direct moral obstacle to its destruction.

Now that Singer's chain of argumentation has been reconstructed step by step, its hidden presuppositions can be identified. The first presupposition, concealed in step two, is the reduction of consciousness to sentience. Without independent argumentation, Singer equates consciousness with the capacity to experience pleasure and pain. However, consciousness can be defined differently. For example, in the Islamic philosophical tradition, consciousness means intuitive knowledge, which is not necessarily accompanied by pleasure or pain. An inanimate object can possess, existentially, intuitive self-awareness without experiencing any pleasure or pain. This alternative definition will be examined in detail in the third section of this study.

The second presupposition, concealed in step three, is methodological physicalism. Singer assumes that consciousness is a physical phenomenon that must have an identifiable material substrate. He then selects the nervous system as the material substrate of consciousness. However, this choice is based on a metaphysical presupposition. There is no conclusive argument proving that consciousness cannot be realized in non-neural substrates as well. Singer simply ignores this possibility.

The third presupposition, concealed in step one, is the condition of consciousness for the moral significance of preferences. Singer argues that only conscious preferences have moral significance because only they are accompanied by suffering. However, this argument rests on a specific theory of value that considers suffering as the sole source of negative moral value. One could have an alternative theory of value according to which the mere existence of an existential tendency—even without emotional consciousness—could be a source of moral value. This discussion will be pursued in the fifth section of this study through the presentation of the principle of the intensity of existence.

The fourth presupposition, which pervades this entire chain of argumentation, is empirical foundationalism. Singer recognizes only knowledge obtained through sensory observation and empirical methods as valid. Hence, he rejects the existence of consciousness in plants and inanimate objects due to the lack of empirical evidence. But this foundationalism is itself a philosophical position requiring justification. Singer has neither justified this position nor seriously examined the possibility of non-empirical forms of knowledge. The important point is that these presuppositions are neither empirical discoveries nor logical necessities. They are philosophical choices. Singer could have made other choices. For example, he could have defined consciousness in a non-sentient manner. He could have rejected methodological physicalism. He could have not considered the condition of consciousness as necessary for the moral significance of preferences. He could have replaced empirical foundationalism with a broader epistemology. But he did not do so. He accepted these presuppositions as unquestioned assumptions and then concluded, on their basis, that plants and inanimate objects lie outside the moral circle.

But can these presuppositions be challenged? The answer to this question is affirmative. Each of these presuppositions is a debatable philosophical position. To challenge them, it is not necessary to abandon Singer's entire theory. Rather, the presuppositions can be criticized one by one and reasonable alternatives can be offered for them. What this study pursues is the critique and replacement of the second presupposition (methodological physicalism) and the first presupposition (the reduction of consciousness to sentience). The proposed alternative is drawn from Mulla Sadra's Transcendent Theosophy.

Before proceeding to the third section, it must be emphasized that the study's critique is not directed at the normative principles of preference utilitarianism. Even if one agrees with the principle of maximizing preferences, one can still reject Singer's definition of consciousness and preference. In other words, the normative component of Singer's theory is separable from its epistemological component. The study's critique is directed at the second component. If a justified alternative definition of consciousness and preference can be offered that is consistent with the foundations of preference utilitarianism and extends the moral circle to inanimate nature, then it can be said that the limitation of Singer's theory is not inherent to utilitarianism itself but arises from his specific epistemological presuppositions.

3. Explication of Knowledge in Transcendent Theosophy

Having identified the epistemological presuppositions of Singer's theory, the time has now come to present an alternative redefinition of knowledge. This redefinition is drawn from Mulla Sadra's Transcendent Theosophy, one of the most profound philosophical systems in the Islamic tradition. The Sadraean redefinition is not only free from the problems of Singer's theory but also provides a basis for extending the moral circle to all levels of existence. In this section, first, Mulla Sadra's critique of the Peripatetic definition of knowledge is presented. Then, his alternative theory is explained, focusing on the concepts of the principality of existence, the gradation of existence, and the union of the knower and the known. Finally, it is shown how this redefinition renders consciousness as a continuous spectrum flowing throughout all of existence.

To grasp the depth of the Sadraean redefinition, one must first understand the rival definition. In Peripatetic philosophy, especially in the intellectual system of Avicenna, knowledge is defined as the impression of the form of an object in the mind. According to this definition, when we know something, a form of that object is imprinted in our mind. This mental form represents external reality. Knowledge in this view is a mental and psychological matter situated opposite the external world. Mulla Ṣadra (2002, vol. 3, p. 280) fundamentally critiques this definition. His main critique is that if knowledge were merely the impression of a form in the mind, there would be no guarantee that this form corresponds to external reality. In other words, how can we be sure that what is imprinted in our mind matches what exists externally? This is the same problem known in Western philosophy as the problem of external reality and idealism.

To avoid this problem, Mulla Sadra offers an alternative theory according to which knowledge is the very presence of the disclosed object before the knower. More precisely, knowledge belongs to the category of existence, not to the category of quiddity. Mulla Ṣadra (2002, vol. 3, p. 290) writes that knowledge is the mode of existence of the disclosed object before the knower. This definition transforms knowledge from a psychological matter into an ontological matter. In this view, the knower and the known are not separate. Rather, knowledge is the very mode of realization of the known before the knower. This is the famous theory of the union of the knower and the known, considered one of the most original doctrines of Mulla Sadra's philosophy (Mulla Sadra, 2025, pp. 130-135).

To understand this theory, attention must be paid to two fundamental principles of Transcendent Theosophy: the principality of existence and the gradation of existence. The principle of the principality of existence states that what truly exists in the external world is existence, and quiddities are merely conceptualizations and appearances of existence. Mulla Ṣadra (2002, vol. 1, p. 50), in opposition to the Peripatetic principality of quiddity, argues that in our immediate experience, we encounter existence, not quiddities. Quiddities such as humanity or animality are abstract concepts that the mind constructs from particular existents. Therefore, what has objective realization in the external world is existence (Mulla Sadra, 2025, p. 18; Tabatabaei, 2011, Vol 3, p. 110-112).

The principle of the gradation of existence complements the principle of the principality of existence. According to this principle, existence is a single, graded reality possessing degrees of intensity and weakness. Mulla Ṣadra (2025, vol. 1, p. 135) explains the gradation of existence using the example of light. Light is a single reality, but its intensity varies across different degrees, from the weak light of a candle to the strong light of the sun. Existence is likewise. The existence of an inanimate object is the weakest degree, the existence of a plant is intermediate, the existence of an animal is stronger, and the existence of a human being is the strongest degree in the natural world. However, the degrees of existence do not end here, for there exist higher degrees of existence beyond the natural world.

With these two principles, the theory of the union of the knower and the known can be explained. If existence is a graded reality, and if knowledge is itself a mode of existence, then knowledge too will have gradational degrees. Mulla Ṣadr (2002, p. 295) argues that knowledge at its highest level becomes identical with the existence of the knower and the known. In other words, when a being attains a high degree of existential perfection, it can unite with other beings and perceive them directly and intuitively. This is the highest level of knowledge, realized in perfect human beings possessing the holy soul. But weaker degrees of knowledge also flow throughout all of existence (Mulla Sadra, 2025, pp. 150-154).

Now we reach the core of the discussion. If knowledge is a mode of existence, and existence has gradational degrees, then every being, to the extent of its existence, possesses a degree of knowledge and consciousness proportionate to that existence. This means that not only humans and animals, but also plants and even inanimate objects possess a kind of knowledge and consciousness. Of course, this knowledge at lower levels of existence is very weak and impersonal. But it is not zero. Mulla Ṣadra (2002, p. 302), in addition to philosophical demonstration, also cites Qur'anic verses to prove this claim. Among them is the noble verse: "There is nothing that does not glorify Him with praise". Glorification is a type of knowledge and consciousness. If inanimate objects engage in glorification, then they must possess some kind of consciousness.

However, it must be noted that this consciousness is essentially different from human consciousness. The consciousness of an inanimate object is neither self-conscious, nor propositional, nor reflective, nor accompanied by pleasure and pain (Abudiyyat, 2001, pp. 159-165). The consciousness of an inanimate object is merely a very weak intuitive knowledge of its own existence and of its origin. It can be called an existential tendency or an impersonal awareness. Mulla Sadra refers to it as instinctive knowledge or innate knowledge that has been entrusted to all beings.

This redefinition of knowledge has profound implications for environmental ethics. The first implication is that beings can no longer be excluded from the moral circle on the basis of lacking a nervous system. For consciousness in this view is not dependent on a nervous system. Consciousness is an ontological matter, not a bio-physical one. The second implication is that consciousness is not a binary phenomenon. It is not a matter of either having consciousness or not. Rather, consciousness is a continuous spectrum. Its weakest degree is realized in inanimate objects, a stronger degree in plants, an even stronger degree in animals, and the strongest degree in human beings. The third implication is that this view leads neither to pseudo-psychism nor to anthropomorphism. Pseudo-psychism claims that everything possesses consciousness to the same degree (Bidhendi, 2015, pp. 65-68). But in this view, consciousness has gradations. Anthropomorphism claims that only human beings are conscious. But in this view, every being is conscious to the extent of its existence.

To clarify further, a comparison can be made between the two definitions of knowledge. In Singer's definition, knowledge is a mental and propositional state dependent on a nervous system. Knowledge in this definition is either present or absent. A being either has a nervous system and is conscious, or lacks it and is unconscious. There is no intermediate state. In the Sadraean definition, knowledge is a mode of existence realized independently of a nervous system. Knowledge in this definition has degrees. Every being possesses knowledge to the extent of its existence. No being is completely unconscious, even if the consciousness of some beings is very weak. "Knowledge is not the impression of the form in the mind; rather, it is a mode of existence of the known thing in the presence of the knower" (Mulla Ṣadra, 2004, Vol. 3, p. 290). This difference in definition entails a difference in the moral circle. In Singer's definition, the moral circle is restricted to beings possessing a nervous system. In the Sadraean definition, the moral circle extends to all beings, from inanimate objects to human beings. Of course, this does not mean that all beings have equal moral value. The moral value of each being is proportionate to its degree of consciousness and intensity of existence. A human being, due to a stronger degree of consciousness, has greater moral value than a plant. But a plant is not without value. A plant possesses moral value proportionate to its degree of consciousness (Mulla Ṣadra, 1987, pp. 268-275).

After explicating the Sadraean redefinition of knowledge, we can now answer the question of whether this redefinition can be incorporated within the framework of Singer's preference utilitarianism. But before proceeding to that section, it is necessary to recall an important distinction. The Sadraean redefinition of knowledge is an ontological theory of consciousness. This theory can be accepted independently of any specific ethical theory. Even someone who does not agree with preference utilitarianism can accept the Sadraean redefinition. However, in this study, we aim to show that even within the framework of preference utilitarianism itself, accepting the Sadraean redefinition can resolve the limitation of the moral circle. This is achieved by changing the epistemological component of Singer's theory without altering its normative component.

The possibility of incorporating the Sadraean redefinition within the framework of preference utilitarianism. After explicating the Sadraean redefinition of knowledge, the time has now come to assess the relationship between this redefinition and Singer's environmental ethical theory. The central question of this section is whether the redefinition of knowledge as a mode of existence can be incorporated within the framework of Singer's preference utilitarianism without altering the normative principles of this theory. Answering this question is important in two respects. The first respect is that it shows that the limitation of Singer's theory does not lie in utilitarianism as a normative theory but rather in his specific epistemological presuppositions. The second respect is that it paves the way for presenting an alternative principle (the intensity of existence as a criterion for moral value) in the fifth section.

To answer this question, a distinction must be made between the two main components of Singer's theory. The first component is the normative component, which states that an action is morally right if and only if the consequences of that action satisfy the preferences of all affected beings to the greatest possible extent. The second component is the epistemological component, which states that preferences belong to conscious beings, and consciousness is identified through the presence of a nervous system and the capacity to experience pleasure and pain. This distinction is necessary because the study's critique is directed at the second component, not the first. In other words, this study does not seek to abandon preference utilitarianism, but rather to revise its epistemological foundations in order to extend the moral circle to inanimate nature.

Now the question arises as to whether the Sadraean redefinition of knowledge can replace the epistemological component of Singer's theory. To answer this, it must be shown that the alternative definition of knowledge entails an alternative definition of preference that remains compatible with the normative principle of utilitarianism. In Singer's theory, preference is defined as a conscious mental state experienced by a being possessing a nervous system. In the Sadraean redefinition, preference can be defined as the existential tendency of every being to preserve and expand the intensity of its own existence. This new definition has three features. The first feature is that it does not make preference dependent on propositional consciousness. The second feature is that it does not tie preference to a nervous system. The third feature is that it makes preference flow throughout all levels of existence, from the weakest degree in inanimate objects to the strongest degree in human beings.

But is this new definition compatible with the normative principle of preference utilitarianism? The answer is affirmative. The normative principle of preference utilitarianism merely states that preferences should be maximized. This principle does not prescribe any specific definition of preference. Any definition of preference that can be meaningfully employed can be incorporated within this principle. Therefore, if it can be shown that the Sadraean definition of preference (the existential tendency to preserve and expand the intensity of existence) is meaningful and measurable, then preference utilitarianism will also work with this new definition. The only difference is that the circle of beings possessing preferences expands, and consequently moral calculations become more complex.

Now we must address the challenges that might be raised by a proponent of Singer. The most important challenge is that the Sadraean definition of preference is not empirically measurable. Singer (1993, p. 114) emphasizes that the criterion for preference must be such that it can be practically determined which beings possess preferences. The criterion of the nervous system and observable behaviors provides such a capability. But how can the Sadraean definition of preference as an existential tendency be practically measured? This challenge is serious and must be answered.

The study's response to this challenge is presented on two levels. On the first level, it can be said that Singer's own criterion is not entirely objective and unproblematic. Whether a particular being possesses a nervous system may be determinable. But whether that being actually has consciousness or merely neural responses without mental content is an issue that cannot be definitively resolved even in the case of other human beings. The problem of other minds in the philosophy of mind has shown that we can never directly access the consciousness of others. Singer himself is compelled to use an analogical argument: a being that is neurally and behaviorally similar to me probably has consciousness like me. Although this analogical argument is reasonable, it has no definitive empirical basis. Therefore, it cannot be claimed that Singer's criterion is completely objective and free from philosophical presuppositions. On the second level, it can be said that the Sadraean definition of preference, although not directly measurable by ordinary empirical tools, can have indirect empirical indicators. One such indicator is self-organizing behavior and system stability. A living being, or even a stable non-living system, exhibits a tendency to preserve its structure against destructive factors. This tendency can be interpreted as a behavioral indicator of an existential tendency. Although this interpretation requires a specific theoretical framework, Singer's own theory also has such a dependence on a theoretical framework.

The second challenge that might be raised is that the Sadraean definition of preference erases the distinction between living and non-living beings. If inanimate objects also have preferences, then no difference remains between a human being and a stone. This challenge is also answerable. The Sadraean redefinition does not erase distinctions among beings; rather, it transforms them from a discrete distinction into a continuous distinction. A human being has a very strong preference, an animal has a moderate preference, a plant has a weak preference, and an inanimate object has a very weak preference. This difference in the intensity of preference will provide the basis for differences in moral value and differences in moral obligations. Therefore, the Sadraean redefinition does not mean equating all beings; rather, it means placing them on a continuous spectrum.

The third challenge is that of philosophical justification. Singer could claim that his definition of consciousness is based on evolutionary biology and neuroscience, whereas the Sadraean definition is based on metaphysics. From Singer's perspective, metaphysics lacks scientific validity and cannot serve as the basis for an ethical theory. The study's response to this challenge is that Singer's own theory is not devoid of metaphysics. His definition of consciousness as a physical phenomenon dependent on a nervous system is a metaphysical presupposition called physicalism. Physicalism is a metaphysical theory concerning the relationship between mind and body, not an empirical discovery. Singer accepts this presupposition without argumentation. Therefore, the difference between Singer and Sadra is not that one is scientific and the other metaphysical. The difference is that one conceals his metaphysical presuppositions while the other makes them explicit.

Having answered these challenges, it can now be concluded that incorporating the Sadraean redefinition within the framework of preference utilitarianism is not impossible. This task requires three changes in the epistemological component of Singer's theory. First change: replacing the definition of knowledge as a mental state with the definition of knowledge as a mode of existence. Second change: replacing the criterion of the nervous system with the criterion of the intensity of existence as an indicator of consciousness. Third change: replacing a discrete understanding of consciousness (presence or absence) with a continuous understanding of consciousness (a spectrum of degrees). These three changes free preference utilitarianism from the limitation that Singer imposed upon it and extend the moral circle to all levels of existence.

But can Singer himself accept these changes? Apparently not, because these changes conflict with his empirical foundationalism. Singer recognizes only knowledge obtained through the empirical method as valid and rejects any metaphysical knowledge. Hence, he will reject the Sadraean redefinition on the grounds that it is metaphysical. However, the important point is that empirical foundationalism itself is a philosophical position that cannot be proven by the empirical method. This is a well-known vicious circle in the philosophy of science: no empirical argument can prove that only empirical knowledge is valid, because this claim itself is a meta-empirical claim. Therefore, Singer cannot rationally justify his empirical foundationalism. He must either accept it as a presupposition (in which case it is no different from accepting Sadraean presuppositions) or abandon it.

From this discussion, it can be concluded that the choice between Singer's definition of knowledge and the Sadraean definition of knowledge is ultimately a philosophical choice. There is no conclusive argument that prefers one over the other except based on presuppositions that themselves require justification. This study does not claim that the Sadraean definition is true and Singer's definition is false. The study's claim is that the Sadraean definition does not have the limitation of Singer's definition and can extend the moral circle in a way that is more consistent with our moral intuitions regarding the protection of inanimate nature. In this respect, the Sadraean definition is a reasonable and defensible alternative.

Following the exposition of the Sadraean redefinition of knowledge as a mode of existence, it is appropriate to briefly address the theory of panpsychism in order to clarify the points of convergence and divergence between these two approaches. Panpsychism in the Western philosophical tradition—particularly in the thought of philosophers such as Bruce Kauffman, Thomas Nagel, and Galen Strawson—is the view according to which all beings, from inanimate objects to human beings, possess some form of consciousness or mentality (Goff, 2019, p. 7). This theory seeks to provide a unified account of the place of consciousness in the natural world by moving beyond Cartesian dualism on the one hand and physicalist reductionism on the other. In this respect, panpsychism shares with Mulla Ṣadra's view the fundamental claim that consciousness is not confined to beings with a nervous system, but rather permeates all levels of existence.

However, there are fundamental differences between the two approaches that should not be overlooked:

First: In panpsychism, consciousness is typically conceived as a fundamental and irreducible property of matter (analogous to mass or electric charge), whereas in Transcendent Theosophy, consciousness is identical with existence and its intensity, and not an accidental property supervening upon matter. In other words, in panpsychism consciousness is treated as a property, whereas for Mulla Ṣadra consciousness is the very mode of the objective realization of existence and belongs to the category of "modes of existence" rather than adventitious attributes.

Second: Panpsychism, in most of its formulations, distributes consciousness uniformly and homogenously across all beings, treating the difference between an inanimate object and a human being as merely quantitative. By contrast, in the Sadraean view, consciousness is not uniform but gradational and intensifying; that is, every being possesses a degree of consciousness proportionate to the intensity of its existence, and this difference in intensity gives rise to a qualitative difference in the type of consciousness. The consciousness of an inanimate object is simple and non-reflective, whereas human consciousness is self-aware, intuitive, and accompanied by intellectual perception. Thus, while Mulla Ṣadra's view converges with panpsychism in terms of comprehensiveness (i.e., the universality of consciousness), it fundamentally diverges from it with respect to gradational hierarchy and the identity of consciousness with the intensity of existence.

Third: The third difference pertains to the epistemological issue. In panpsychism, the question typically arises as to how one can speak of consciousness in beings lacking a nervous system when we have no empirical access to it. In Transcendent Theosophy, however, the intuitive apprehension of existence—which is existential consciousness—is established not through sensory experience but through philosophical demonstration and the principle of Basīṭ al-Ḥaqīqah (the principle that the simple reality is all things). Mulla Ṣadra, relying on this principle, demonstrates that every being, to the extent of the breadth of its existence, possesses knowledge of its own essence and of its origin, and this knowledge is neither sensory nor conceptual- discursive, but rather a knowledge by presence and existential in nature (Mulla Ṣadra, 2002, vol. 3, p. 302). This aspect places panpsychism—which is largely grounded in physicalist or phenomenological considerations—in an epistemological position fundamentally different from that of Transcendent Theosophy.

Therefore, it can be said that although Mulla Ṣadra's view superficially agrees with panpsychism regarding the universality of consciousness, it differs substantively from it in terms of ontology, gradational hierarchy, and epistemology. These differences ensure that Mulla Ṣadrā's view is not only immune to the charge of panpsychism but can also, by preserving the gradational hierarchy of existence, offer a more precise and more philosophical account of the scope of consciousness and, consequently, of the scope of the moral circle.

4. The Principle of the Intensity of Existence

This principle is directly derived from the redefinition of knowledge in Transcendent Theosophy and provides an answer to the problem of the moral value of inanimate nature. In this section, first, we formulate the aforementioned principle precisely. Then, we extract its ontological and epistemological foundations from Transcendent Theosophy. Subsequently, we explain the three distinctive features of this principle, namely continuity, non-reduction to pseudo-psychism, and transcending anthropocentrism. Finally, we show how this principle can replace Singer's criterion of sentience.

The principle of the intensity of existence can be formulated as follows: the moral value of every being is directly proportional to the degree of intensity of existence of that being, and the intensity of existence is identical to the degree of existential consciousness. In other words, the greater the intensity of a being's existence, the greater its existential consciousness, and consequently the greater its moral value. Conversely, the weaker the intensity of existence, the lesser its existential consciousness and moral value. This principle has two main components. The first component is an ontological component, which states that existence has degrees of intensity and weakness. The second component is an axiological component, which states that the intensity of existence is directly related to moral value.

To understand the foundations of this principle, we must return to two fundamental rules of Transcendent Theosophy: the principality of existence and the gradation of existence. According to the principality of existence, what truly exists in the external world is existence, and quiddities are merely abstract concepts of the mind. (Mulla Ṣadra, 2002, p. 50) proves that in our immediate experience, we encounter existence, not quiddities. This rule means that the difference among beings is not a difference in quiddity but a difference in the intensity and weakness of existence. According to the gradation of existence, existence is a single graded reality possessing degrees of intensity and weakness. (Mulla Ṣadra, 2002, p. 135) compares existence to light, which is a single reality but has various degrees of intensity and weakness. From the weakest degree of existence in inanimate objects to the strongest degree in human beings and beyond, there exists a continuous spectrum. Now, if we redefine knowledge as a mode of existence (as was explained in detail in the third section), then knowledge will also have gradational degrees. (Mulla Ṣadra, 2002, p. 295) specifies that knowledge is the mode of existence of the disclosed object before the knower. Hence, every being, to the extent of its existence, possesses a degree of knowledge proportionate to that existence. This knowledge can, at higher levels, lead to intuitive knowledge and union with the known, and at lower levels, be realized as an instinctive and impersonal knowledge. But in any case, no being is completely devoid of knowledge and consciousness. Even inanimate objects, to the extent of their weak existence, possess a kind of existential consciousness.

With these preliminaries, the principle of the intensity of existence can now be formulated as a principle of environmental ethics. This principle tells us that all beings, from inanimate objects to human beings, possess moral value, but their moral value is not equal (Bidhendi et al., 2015, p. 145). Every being has moral value to the extent of the intensity of its existence. Several important conclusions follow from this principle. The first conclusion is that the human being possesses the highest moral value among natural beings, because the intensity of his existence is greater than that of all other natural beings. The second conclusion is that animals possess higher moral value than plants, because the intensity of their existence is greater. The third conclusion is that plants possess higher moral value than inanimate objects. The fourth conclusion is that inanimate objects are not without value, even if their moral value is very weak.

The first feature of the principle of the intensity of existence is its continuity. Unlike Singer's criterion of sentience, this principle creates a continuous spectrum of moral value. In Singer's criterion, there is a discrete gap between beings possessing a nervous system (possessing moral value) and beings lacking a nervous system (lacking moral value). This gap is absolutely unbridgeable. No matter how complex a plant may be, because it lacks a nervous system, it has no direct moral value. But in the principle of the intensity of existence, no such gap exists. The difference between an inanimate object, a plant, an animal, and a human being is a difference in degree, not a difference in kind. Hence, the principle of the intensity of existence is more consistent with our moral intuitions. Our moral intuition tells us that a tree has greater moral value than a stone, and a dog has greater moral value than a tree. The principle of the intensity of existence justifies this intuition, whereas Singer's criterion cannot attribute any direct moral value to a tree.

The second feature of the principle of the intensity of existence is that it is not reducible to pseudo-psychism. Pseudo-psychism, or panpsychism, is the theory according to which all beings possess consciousness, and this consciousness is identical everywhere (Koch, 2014, p. 1). This theory faces numerous philosophical problems, including that it does not explain the obvious difference between a human being and a stone. However, the principle of the intensity of existence is fundamentally different from pseudo-psychism. In pseudo-psychism, consciousness is an identical, ubiquitous phenomenon. In the principle of the intensity of existence, consciousness is a spectrum of degrees. The consciousness of a human being differs essentially from the consciousness of a stone, not merely in intensity. But this essential difference itself arises from the difference in the intensity of existence. In other words, the intensity of existence creates such a difference that consciousness at different levels acquires different qualities. Therefore, the principle of the intensity of existence not only does not entail pseudo-psychism; in fact, it is the very opposite. Pseudo-psychism renders consciousness uniform and flat, whereas the principle of the intensity of existence regards consciousness as gradational and hierarchical.

The third feature of the principle of the intensity of existence is that it transcends anthropocentrism. Anthropocentrism means placing the human being at the center of the moral universe and valuing other beings solely based on their utility for human beings (Pentreath, 2004, p. 21). Although Singer's criterion goes beyond anthropocentrism and includes animals, it remains trapped within a broader form of anthropocentrism. Because it completely excludes beings lacking a nervous system from the moral circle. This is what can be called sentiocentrism, that is, a kind of extended anthropocentrism that has shifted the boundary from humans to sentient animals. But the principle of the intensity of existence goes even beyond this. According to this principle, no being is outside the moral circle. All beings, including inanimate objects, possess moral value. Of course, the moral value of inanimate objects is very weak, but it is not zero. This approach is consistent with Eastern spiritual traditions as well as with some Western philosophical traditions.

Now it can be shown how the principle of the intensity of existence replaces Singer's criterion of sentience. In Singer's theory, a moral action must maximize the preferences of all sentient beings. In the theory proposed by this study, a moral action must maximize the preferences of all beings, considering the intensity of their existence. This change has two important implications. The first implication is that moral calculations become more complex, because more beings must be considered. However, this complexity is resolved by the principle of proportionality: every being has weight in moral calculations to the extent of the intensity of its existence. A being with a very weak intensity of existence (such as a stone) will have a very negligible weight in moral calculations. But its weight is not zero. Therefore, in cases where there is a conflict between the interests of a stone and the interests of a human being, the interests of the human being will naturally be preferred. However, in cases where there is a conflict between the interests of a stone and the interests of no other being, even that negligible weight can be decisive. For example, destroying an ancient rock formation solely for aesthetic pleasure, even if no animal or plant is endangered, is morally wrong because it disregards the weak preference of that rock formation to preserve the intensity of its own existence.

The second implication is that the principle of the intensity of existence is more consistent with our moral intuitions about environmental protection. Our moral intuition tells us that an ancient forest has direct value, not merely because of the animals living in it. The principle of the intensity of existence justifies this intuition, because the trees and even the soil and stones of that forest also possess moral value, however weak. Likewise, our moral intuition tells us that an endangered species, even if the last surviving member of that species lacks a nervous system (for example, a particular species of plant), has a value worth protecting. The principle of the intensity of existence also justifies this intuition. It must be emphasized that the principle of the intensity of existence is not merely a practical rule for moral decision-making, but rather an ontological theory concerning the relationship between existence, consciousness, and value. This theory claims that these three categories ultimately reduce to a single reality. Existence, consciousness, and value are three degrees of one reality. The greater the intensity of existence, the greater the degree of consciousness and the greater the moral value. This theory has profound implications not only for environmental ethics but for the whole of moral philosophy. For if consciousness flows throughout all existence, then no being can be completely excluded from the moral circle. This means that environmental ethics becomes the ethics of all existence.

5. Conclusions

This study has demonstrated that the limitation of Peter Singer's environmental ethical theory in attributing moral value to inanimate nature stems from his specific definition of knowledge and consciousness. By reducing consciousness to sentience and tying it to the presence of a nervous system, Singer a priori excludes beings lacking a nervous system from the moral circle. However, this definition is not an empirical discovery but a philosophical choice that Singer has accepted without sufficient justification. His theory, rather than being based on the nature of reality, rests on specific epistemological presuppositions that are themselves contestable. In contrast, Mulla Sadra's Transcendent Theosophy offers an alternative definition of knowledge in which knowledge is defined as a mode of existence. According to the two principles of the principality of existence and the gradation of existence, every being, to the extent of the intensity of its existence, possesses a proportionate degree of consciousness. This consciousness is very weak and impersonal in inanimate objects, but it is not zero. Consciousness in this view constitutes a continuous spectrum from the weakest degree in inanimate objects to the strongest degree in human beings. This redefinition, unlike Singer's definition, does not exclude beings lacking a nervous system from the circle of consciousness.

The study has also demonstrated that this Sadraean redefinition can be incorporated within the framework of Singer's theory without altering the normative principles of preference utilitarianism. It is sufficient to redefine preference from conscious preference to the existential tendency of every being to preserve and expand the intensity of its own existence. In this way, preference utilitarianism is freed from its inherent limitation and the moral circle is extended to all levels of existence. The main achievement of this study is the principle of the intensity of existence as a criterion for moral value. This principle states: the moral value of every being is directly proportional to the degree of intensity of existence of that being, and the intensity of existence is identical to the degree of existential consciousness of that being. This principle has three distinctive features. First, continuity; unlike Singer's discrete criterion, it delineates a continuous spectrum of moral value from inanimate objects to human beings. Second, non-reduction to pseudo-psychism; unlike pseudo-psychism, which posits consciousness as identical and ubiquitous, it emphasizes differences in the degrees of existence and consequently differences in the degrees of consciousness. Third, transcending anthropocentrism; unlike anthropocentrism and even sentiocentrism, it includes all beings, including inanimate objects, within the moral circle.

Several general conclusions derive from this study. First, every environmental ethical theory is inevitably grounded in an epistemological theory and ultimately in an ontological theory. Therefore, one cannot determine the moral circle without taking a position on the nature of knowledge and consciousness. Second, the definition of knowledge as a mental and propositional state dominant in Western philosophy creates serious limitations for environmental ethics, and there is a need to rethink this definition. Third, non-Western philosophical traditions such as Transcendent Theosophy can serve as rich resources for solving contemporary problems in moral philosophy, and they should not be regarded merely as historical or anthropological subjects. Finally, this study has shown that the contemporary environmental ethical crisis is not merely a normative crisis but, more deeply, an epistemological crisis. As long as our definition of knowledge and consciousness is restricted to beings possessing a nervous system, we cannot attribute direct moral value to inanimate nature. However, by redefining knowledge as a mode of existence and accepting the truth that consciousness flows in all levels of existence to varying degrees, a new horizon can be opened in environmental ethics. A horizon in which no being is outside the moral circle, and all beings, from inanimate objects to human beings, each to the extent of the intensity of its existence, are worthy of moral respect and care. This is not merely a philosophical theory, but an invitation to a transformation in the human relationship with the natural world; a world in which every being, to the extent of its existence, possesses consciousness and value.