The Zombie Argument Against Physicalism

The philosophical objection to physicalism commonly referred to as the “zombie argument” has been increasingly well-known since the 1990s among academic philosophers and specialists in metaphysics. David Chalmers has done much to popularize this argument. Chalmers provides a logical critique of physicalism that is solid in nature. Yet the “zombie argument against physicalism” is sometimes difficult for laypeople to grasp even as it has become a common line of thought in the practice of philosophy. This paper will provide a comprehensive overview of the nature of physicalism as an approach to metaphysical thought, and then proceed to explain the inherently problematic nature of physicalism by utilizing the zombie argument.

An Overview of Physicalism

Physicalism is an ontological concept which suggests that nothing exists beyond the physical. It is a perspective that is both materialist and monist in nature. Physicalists normally rely on a theoretical foundation for their position that is rooted in the discipline of physics. In this regard, a physicalist may either draw from the actual field of physics as it is conceived of at a particular time or postulate an ideal form of physics of their own. Such a theoretical framework raises the problem of Hempel’s dilemma, as Hempel suggested the fallacy of utilizing theory as an analytical methodology for postulating the nature of the physical. Simply, if an understanding of the physical is sought by means of referring to the current state of thought regarding physics itself, then physicalism is likely to be untrue as the field of physics at any one juncture is likely to contain many fallacies due to the limitations in human understanding.

Likewise, if the physical is to be understood in terms of some idealized conception of physics, then physicalism simply lacks any substantive mode of thought which can be critically understood. However, the theory-based foundation offered by some physicalists is rejected by others. An alternative perspective may be object-based rather than theory-based. An object may be defined as physical by its very nature. For instance, an automobile is physical because of its nature as an object. This perspective has sometimes been referred to as “pan-physicism” or “pan-protophysicism.” It can also be argued that the physical can simply be defined in terms of what it is not, such as the mental or the spiritual.

A physicalist regards the physical or the material to be the sum total of all things, or “all that there is.” According to physicalists, the metaphysical is subordinate to the material. Physicalists explain this according to the principle of supervenience. In terms of its practical application, physicalism claims that the world as human beings perceive it is solely material in nature, and that all possible worlds must also be material in nature. The probability and possibility of the supernatural or the extra-physical are then discounted or denied. For instance, if extraterrestrial life were found to be in existence on other planets, such forms of life would likewise be material or physical in nature out of metaphysical necessity. Such a framework might also be applied to an understanding of the progression of time. Any conceivable chain of events occurring within the framework of time and space, or any alternative chain of events that might have transpired, must also be physical in nature. Placed in a theological context, physicalism in many ways resembles the ideas of the classical deists of the Enlightenment Period who postulated a God who established physical laws, and then stepped aside and allowed those laws to operate in a mechanistic sense.

A similar line of argument in the defense of physicalism is the claim that all properties contained within the world must not be capable of being duplicated in a way that would contain elements of the non-physical. Yet this perspective becomes problematic as a world can be conceived of where the balance between the physical and non-physical is either indeterminate or proportionally arranged in such a way that that the distinctiveness of each becomes incomprehensively blurred, or where the level of dominance of the physical over the non-physical is such as to constitute limits on the totality of the physical. Some opponents of physicalism, particularly traditional theists, will raise an objection rooted in what has been called the necessary beings argument. According to this argument, it is ontologically possible to conceive of a being or beings whose nature(s) is non-physical that would exist in any concept of material or extra-material reality. If indeed such entities were found to be in existence, the claims of physicalism would be canceled.

Physicalists are divided between proponents of a priori physicalism and a posteriori physicalism. The former argues that physicalism can be validated independently of human experience, while the latter claims that physicalism is validated in a way that is legitimated by experience. Proponents of a priori physicalism acknowledge the intersectional nature of truth. One truth is connected to all other truths. However, adherents of a posteriori position argue for the possibility of truths that can be conceived of beyond those of observable realities, or which are validated by virtue of their occurrence within the realm of experience. The essence of the physicalist perspective was summarized by Albert Einstein who suggested that the sum total of all reality is contained within the laws of theoretical physics.

The Zombie Argument Against Physicalism

A so-called “philosophical zombie” is a concept found within the metaphysical subcategory of philosophy that deals with matters of mind and perception. The term “zombie” used in this context is a proposed hypothetical entity that lacks consciousness or sentience as human beings possess or conceive of these things. A “zombie” may mimic the human experience even though the zombie does not actually undergo the experience in question as part of its own reality. Metaphysicians have developed the concept of a “philosophical zombie” to argue against the various kinds of physicalism. These include materialism, behaviorism, and functionalism. The essence of the physicalist thinking is that all reality may be explained in materialist terms and that all human experience is a product of biological and neurological functioning. Physicalists deny the existence of the “spiritual,” the “human soul,” and so forth. A debate has emerged in recent years between thinkers who use the zombie argument in order to formulate a critique of physicalism, such as David Chalmers, and those who deny the logical coherence of the zombie argument, such as the well-known “new atheist” writer Daniel Dennett.

According to physicalists, elements of the human being such as conscious thought, desire, will, feelings, emotions, etc. are merely physical in nature and have purely material causes. The concept of “philosophical zombies” originates from philosophers seeking to utilize the popular concept of a “zombie” as the basis for an argument against physicalism. Anti-physicalists will conduct thought experiments postulating multiple kinds of zombies: behavioral, neurological, and soulless. The first of these behave in the same manner as a human being. The second possesses a human brain and likewise exhibits ordinary human behavior. The latter simply lacks a soul in the spiritual or metaphysical sense.

Zombie arguments are used by philosophical opponents of physicalism to demonstrate the possibility of a legitimate differentiation between the mental and the physical, or the material and the spiritual. The zombie argument is a sub-category of modal arguments against physicalism. Arguments of this type have been advanced by Saul Kripke, Thomas Nagel, and Robert Kirk, although it is Chalmers who has offered the most advanced rendition of this argument. Chalmers believes that it is possible for the individual to conceive of a world that is entirely inhabited by zombies. This would be a world where the physical appearance of all material matter would be indistinguishable from that of the world as it presently exists. The human zombies that would inhabit such a world would lack consciousness. From this thought experiment, Chalmers has cultivated a sophisticated and comprehensive argument against physicalism.

If physicalism is true, then everything that exists in the realm of human experience is physical in nature. Even consciousness itself would be within the realm of the physical. In an alternative world that would be possible in a metaphysical sense, the physical nature of such a world must contain all the same physical properties and exhibit the same physical characteristics as the actual world. These properties would have to include the possibility of consciousness and conscious experience. However, it is possible to conceive of an alternative world where all of the physical attributes of the actual world are present, and yet consciousness does not exist. Instead, such a world would be populated by zombies. However, such as the world would be logically impossible from a metaphysical perspective. Therefore, physicalism cannot be philosophically defended on either logical or metaphysical grounds.

There can be no way of logically denying the validity of arguments such as those formulated by Chalmers. Indeed, a survey of the responses offered to Chalmers and other anti-physicalists by proponents of physicalism illustrates the weaknesses of their perspective. For instance, some have attempted to counter Chalmers’ arguments by suggesting that the alternative world conceived of by Chalmers is impossible. Yet Chalmers points out that there is no logical incoherence involved in his thought experiment. Others have developed the circular argument that the physical world must be defined in terms of the physical. But this argument merely asserts what it wishes to prove. Still, others have claimed the metaphysical impossibility of the zombie world. Chalmers has effectively defended his thought experiment on ontological grounds and pointed out that whatever is logically possible is also metaphysically possible.

Dennett has offered what is perhaps the most sophisticated reply to the zombie argument. He suggests that the realm of the human experience cannot be divorced from the realm of the physical, noting that the experience of pain, in particular, is relative to the neurobiological composition of the human being. A zombie would simply be unable to experience pain because the nature of a zombie would be such as to make pain impossible. However, Dennett’s objection is not ontologically defensible. The fact that it is possible to conceive of a world populated by zombies capable of experiencing pain indicates both the logical and metaphysical possibility of such. Further, even within the realm of actual human experience there are various beings that lack consciousness but are capable of experiencing pain such as animals. Clearly, the human capacity for consciousness cannot be explained by purely neurobiological or physical terms. The zombie argument against physicalism holds up to the scrutiny of its critics.

Physicalism postulates that human beings exist within a spiritless and soulless universe. Materialism denies essential elements of what it means to be human, such as the importance of the non-rational. It is the spirit that gives meaning to existence. The zombie argument ironically provides a thought experiment that allows the introspective person to examine what a world without the spiritual would be. It would indeed be a world of zombies who functioned only as automatons responding to stimuli. It is the spiritual, the soul, and the non-rational which allow the human being to rise above the level of animals acting only according to instinct. In a materialist universe, humans would be zombies, indeed. Therefore, a perspective as seemingly esoteric as the zombie argument against physicalism reflects a wider set of ideas which are of immense importance. The zombie argument against physicalism challenges the philosopher to embrace the transcendent. It is this transcendence that gives existence its meaning and allows for aspirations to higher ideals such as justice, truth, and virtue. 

Bibliography

Chalmers, D. The Conscious Mind: In Search of a Fundamental Theory. New York and Oxford: Oxford University Press; 1996.

Dennett, D. The unimagined preposterousness of zombies. Journal of Consciousness Studies. 1995; 2 (4), 322–326.

Kripke, S. Naming and necessity. In: Davidson, D. and Harman, G., editors. Semantics of Natural Language. Dordrecht, Holland: Reidel, 1972: 253–355.

Nagel, T. Armstrong on the mind. Philosophical Review. 1970; 79, 394–403.