Physicalism

In metaphysics, physicalism is the philosophical stance asserting that all phenomena are fundamentally physical, that no entities exist beyond the physical realm, and that all properties supervene upon physical properties. This position contrasts sharply with idealism, which postulates that reality is fundamentally mental. Physicalism constitutes an ontological monism, positing a singular fundamental substance, unlike dualistic (mind–body dualism) or pluralistic perspectives that propose multiple substances. It shares significant commonalities with naturalism, despite notable differences.

Physicalism bears a close relationship to materialism, from which it evolved as physical sciences advanced their explanations of observed phenomena. The terms "physicalism" and "materialism" are frequently employed synonymously, yet they can be differentiated by recognizing that physics encompasses more than merely matter. Physicalism extends beyond matter to include concepts such as energy, physical laws, space, time, spacetime, exotic matter, structure, physical processes, information, states, and forces, as delineated by physics and other scientific disciplines.

A 2020 survey indicated that physicalism constitutes the prevailing viewpoint among philosophers, with 51.9% endorsement, though it also faces considerable opposition.

Beyond the philosophical domain, physicalism may denote the conviction that physics offers the most effective, or indeed the sole, means of apprehending truth concerning the world or reality.

Defining Physicalism within Philosophy

The term "physicalism" was formally introduced into philosophical discourse during the 1930s by Otto Neurath and Rudolf Carnap.

Within the framework of physicalism, the term "physical" functions as a philosophical concept and is distinct from alternative definitions present in scholarly literature (for instance, Karl Popper characterized a physical proposition as one theoretically falsifiable by observation). In this specific context, a "physical property" might represent a metaphysical or logical composite of properties not conventionally considered physical. The concept of supervenience is frequently employed to articulate this idea of a "metaphysical or logical combination of properties." Supervenience posits that no two events can be identical in all physical attributes yet diverge in any mental attribute, nor can an object undergo a mental alteration without a corresponding physical change. The introduction of supervenience is necessitated by the physicalist assumption that various abstract concepts, not ordinarily considered physical, nonetheless exist.

Type-Identity Physicalism

Type-identity physicalism, alternatively termed the mind-body identity theory, asserts that mental events are classifiable into types that correspond directly with specific types of physical events. For example, a particular mental event type, such as pain, is posited to correlate with a specific physical event type, such as the firing of C-fibers. According to this perspective, every occurrence of pain invariably corresponds to instances of C-fiber activation. Consequently, type-identity physicalism is characterized by the assertion of an identity between types: every mental type is considered identical to some physical type.

A prevalent objection to type-identity physicalism is the challenge posed by multiple realizability. Multiple realizability theorizes that an identical mental state can be instantiated by diverse physical states. This concept implies a many-to-one mapping from physical states to mental states.

Token-Identity Physicalism

Token-identity physicalism asserts that each individual mental event constitutes a specific physical event (a token physical event), yet without a corresponding type-to-type mapping between mental and physical events. Davidson's anomalous monism serves as the most frequently cited illustration of token-identity physicalism. A key advantage of token-identity physicalism lies in its compatibility with the principle of multiple realizability. Consequently, mental states like pain can be instantiated by a multitude of disparate physical events, even in the absence of any typological resemblance among these physical occurrences.

Reductive and Non-Reductive Forms of Physicalism

The Concept of Reductionism

Within the philosophy of mind, reductionism is generally conceptualized as the process of reducing psychological phenomena to fundamental principles of physics and chemistry. Simplistically, reductionism posits that a system is exhaustively defined by the aggregate of its constituent components. Physicalism encompasses both reductive and non-reductive iterations. Reductive physicalism specifically maintains that mental states are not ontologically distinct from physical states and are, therefore, reducible to them.

The Concept of Emergence

Emergentism, a theory that gained prominence in the early 20th century, posits that a system's emergent properties arise as novel outcomes from the interaction of its constituent properties, yet are distinct from them. Strong emergence concepts frequently appear in discussions of non-reductive physicalism. This philosophical stance underscores the idea that the whole transcends the mere sum of its parts. Within the philosophy of mind, emergence is frequently associated with property dualism.

Critiques of Physicalism

The Knowledge Argument

Historically, numerous objections have been raised against physicalism, with many focusing on the perceived inconsistency of qualia existing within a purely physical world. Among these, the most widely recognized is the knowledge argument, articulated by Frank Jackson and famously presented as "Mary's room."

This argument presents the hypothetical scenario of Mary, a woman confined to a black-and-white room, experiencing the world solely through a monochrome television monitor throughout her life. Despite her access to comprehensive physical knowledge, including all physical facts pertaining to color, a physicalist perspective would suggest that Mary possesses complete knowledge of the world. However, upon her release into the world, it becomes evident that Mary lacked certain knowledge, specifically the feeling or experience of perceiving color. This raises the question: if Mary lacked such knowledge, how can the supervenience of everything upon the physical be maintained?

Physicalist Responses

One counter-argument, formulated by Lawrence Nemerow and David Lewis, is termed the ability hypothesis. This hypothesis differentiates between propositional knowledge, exemplified by "Mary knows that the sky is typically blue during the day," and practical knowledge, such as "Mary knows how to climb a mountain." It asserts that Mary's acquisition from experiencing color is solely practical knowledge. Consequently, this response posits that while Mary does gain knowledge from her experience, it does not constitute the propositional knowledge necessary for the logical validity of the knowledge argument.

The Philosophical Zombie Argument

A frequent challenge to both a priori physicalism and physicalism broadly is the "conceivability argument," also known as the zombie argument. This argument proceeds approximately as follows:

1. Physicalism asserts that all phenomena in our world, including consciousness, are fundamentally physical.
2. Consequently, if physicalism holds true, a metaphysically possible world identical to the actual world in all physical facts would encompass everything present in the actual world. Specifically, conscious experience would exist in such a world.
3. It is conceivable to imagine a world physically identical to our own but devoid of consciousness—a "zombie world." This conceivability implies the metaphysical possibility of such a world.
4. Therefore, physicalism is false. (This conclusion is derived from premises (2) and (3) via modus tollens.)

The potential existence of philosophical zombies (p-zombies) implies that mental states do not supervene on physical states, thereby refuting physicalism. David Chalmers, an Australian philosopher, contends that the conceivability of a zombie establishes its metaphysical possibility.

Physicalist Responses

Galen Strawson asserts that the conceivability of zombies cannot be established, rendering the argument invalid due to the absence of its foundational premise.

Daniel Dennett contends that philosophers who assert the conceivability of zombies consistently underestimate the cognitive demands of conception or imagination, ultimately envisioning entities that contradict their own definitions. He introduced the term "zimboes"—p-zombies possessing second-order beliefs—to argue for the incoherence of p-zombies, stating: "Zimboes think^Z they are conscious, think^Z they have qualia, think^Z they suffer pains—they are just 'wrong' (according to this lamentable tradition), in ways that neither they nor we could ever discover!" In his 1995 work, The Unimagined Preposterousness of Zombies, Dennett draws an analogy between consciousness and health.

The hypothetical removal of consciousness, while preserving all cognitive systems—a common but fundamentally flawed imaginative exercise—is analogous to postulating the removal of health while leaving all bodily functions and capabilities unimpaired. Neither health nor consciousness can be conceptualized in such a separable manner.

Michael Lynch contends that the philosophical argument for zombie conceivability compels a choice between doubting the existence of our own consciousness and affirming the impossibility of zombies. If zombies erroneously perceive themselves as conscious, the certainty of our own conscious experience becomes questionable. We might mistakenly believe in conscious mental states when, in reality, we merely harbor a false conviction. Lynch posits that refuting the possibility of zombies constitutes a more rational stance than challenging the reality of our own consciousness.

Daniel Stoljar has introduced "the phenomenal concept strategy," which posits that only the concept of consciousness, rather than the property itself, possesses a unique or sui generis character.

Hempel's Dilemma

Traditionally, physicalists have adopted a "theory-based" definition of the physical, grounded in either contemporary physics or a prospective (ideal) future physics. Hempel's Dilemma, named after the philosopher of science Carl Gustav Hempel, challenges physicalism by asserting the inherent problems with both methodologies. Should the physical be defined by current physics, physicalism is highly probable to be erroneous, given the strong likelihood (supported by pessimistic meta-induction) that substantial portions of contemporary physics are incorrect. Conversely, if the physical is characterized by a future (ideal) or complete physics, then physicalism becomes unacceptably vague or indeterminate.

Physicalist Response

Certain physicalists, including Andre Melnyk, embrace the first premise of the dilemma, acknowledging that the current definition of physicalism is highly likely to be inaccurate, provided it remains more plausible than any existing alternative proposition, such as dualism. Melnyk asserts that this perspective mirrors the general scientific attitude toward theoretical frameworks. For instance, proponents of evolutionary theory might concede that its present formulation is subject to future revision, yet they defend it based on the conviction that current evolutionary theory surpasses any contemporary rival concept, such as creationism. Consequently, Melnyk advocates for defining physicalism in relation to contemporary physics and adopting a similar epistemic stance regarding its veracity as scientists typically hold toward currently accepted scientific theories.

Other physicalists advocate for physicalism through alternative conceptualizations. Frank Jackson, for instance, has proposed an "object-based" understanding of the physical. David Papineau and Barbara Montero have advanced a "via negativa" characterization, which fundamentally defines the physical by what it excludes: the mental. Thus, the via negativa strategy interprets the physical as the non-mental.

Argument from Overdetermination

Jaegwon Kim raises an objection to non-reductive physicalism, grounding his critique in the problem of overdetermination. He postulates that M1 causes M2 (representing mental events) and P1 causes P2 (representing physical events). Furthermore, M1 is supervenient upon P1 (meaning P1 realizes M1), and M2 is supervenient upon P2 (meaning P2 realizes M2). If both P1 causes P2 and M1 causes M2, this scenario constitutes causal overdetermination. To circumvent this overdetermination, either M1 or P1 must be eliminated as a cause of P2. Given the principle of the causal closure of the physical, M1 is necessarily excluded. Consequently, the non-reductive physicalist faces an unavoidable choice between two undesirable alternatives: accepting overdetermination or adopting epiphenomenalism. Kim therefore asserts that mental causation can only be maintained through the adoption of a reductionist perspective, wherein mental properties are deemed causally efficacious by virtue of their reduction to physical properties.

Argument from First-Person Perspectives

Christian List contends that the existence of first-person perspectives—where an individual exists as themselves rather than another—refutes physicalism. He argues that since first-personal facts cannot supervene on physical facts, this challenges not only physicalism but also most forms of dualism characterized by purely third-personal metaphysics. List further posits a "quadrilemma" for theories of consciousness, suggesting that a maximum of three among the following metaphysical claims can be simultaneously true: "first-person realism," "non-solipsism," "non-fragmentation," and "one world," thereby implying that at least one must be false. To reconcile the subjective nature of consciousness without lapsing into solipsism, he has proposed a model he terms the "many-worlds theory of consciousness." These concepts are related to the profound question advanced by Benj Hellie.

Alternative Perspectives

Realistic Physicalism

Galen Strawson's concept of realistic physicalism, also known as realistic monism, posits that physicalism inherently implies panpsychism, or at minimum, micropsychism. Strawson contends that "many—perhaps most—of those who identify as physicalists or materialists [erroneously] subscribe to the proposition that physical matter is, fundamentally and intrinsically, entirely non-experiential... even when they acknowledge, as Eddington did, that physical matter possesses, inherently, 'a nature capable of manifesting itself as mental activity,' meaning experience or consciousness." He argues that since experiential phenomena purportedly cannot emerge from entirely non-experiential phenomena, this drives philosophers toward substance dualism, property dualism, eliminative materialism, and "all other misguided endeavors for comprehensive mental-to-non-mental reduction."

Proponents of genuine physicalism must acknowledge that a subset of fundamental constituents inherently involves experience. They are compelled to adopt at least micropsychism. Considering that all concrete entities are physical, that all physical entities are composed of fundamental physical ultimates, and that experience constitutes a component of concrete reality, this position appears to be the sole rational stance, transcending a mere 'inference to the best explanation.' Micropsychism does not equate to panpsychism, as realistic physicalists can currently hypothesize that only specific types of ultimates are intrinsically experiential. However, they must concede the potential veracity of panpsychism, with micropsychism—the acceptance that at least some ultimates must be experiential—representing a significant preliminary step. Strawson suggests that if 'the inmost essence of things were revealed,' the notion that some but not all physical ultimates are experiential would resemble the idea that some but not all physical ultimates are spatio-temporal (assuming spacetime is a fundamental aspect of reality). He expresses strong skepticism regarding such profound heterogeneity at the most fundamental level of existence. Indeed, he later revised his perspective, finding it challenging to distinguish why this view would not be considered a form of dualism. Consequently, he asserts that physicalism, specifically genuine physicalism, necessitates panexperientialism or panpsychism. He posits that all physical matter, in its various energetic forms, is an experience-involving phenomenon. While initially perceiving this idea as unconventional, he has since become accustomed to it, recognizing it as the only alternative to 'substance dualism.' Therefore, authentic physicalism, or realistic physicalism, implies panpsychism, and any challenges arising from this implication must be confronted by a true physicalist.

Cognitive science

• Cognitive science
• Consciousness
• Empiricism
• Epiphenomenalism
• Hempel's Dilemma
• Mary's Room
• Metaphysical naturalism
• Monism
• Multiple realizability
• Naturalism (Philosophy)
• Ontological pluralism
• Philosophy of mind
• Primary–secondary quality distinction
• Reductionism
• Supervenience
• Unphysical

Notes

References

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