Physicalist theories of mind claim that all mental states are correlative to or supervenient on physical states. Functionalism is the physicalist view of the mind that mental states can be defined as functional roles within an organism — the ‘function’ of pain isn’t just to cause behavioural output (as behaviourism might claim), but to cause other mental states also — the belief that I am in pain, and the desire for the pain to stop. In this way, functional mental states are defined by their causal relationship with other mental states (beliefs, desires), sensory inputs, and behavioural dispositions; by the role they play in the wider cognitive system.
Hilary Putnam, an advocate of functionalism, considers the argument of circularity (posed as an objection to behaviourism) and the argument of multiple realisability (posed as an objection to type-identity theory) as supporting functionalism, as it is able to adequately respond to these objections where the aforementioned alternatives cannot. Despite this initial success, this essay will argue functionalism does not give a convincing account of mental states, as it cannot respond to the objections of inverted qualia, and the existence of qualia in general.
Putnam first poses the circularity objection to behaviourism as an argument for functionalism. Behaviourism is the physicalist theory of mind which claims that all mental states are reducible to behavioural outputs (Hempel’s hard behaviourism) or, less strictly, that all propositions about mental states are actually propositions about behavioural dispositions (Ryle’s soft behaviourism). The fact that the same mental state can be realised by almost any behaviour; that being in pain may be analysed by saying ‘ouch!’, but this analysis is not sufficient, as we must also factor in other mental states, such as the self-consciousness or embarrassment of ‘looking like a wimp’. Either the reduction of all mental states to behavioural dispositions is too simplistic, or becomes circular when we consider a behavioural explanation for the other mental states which arise given an analysis of the first. Therefore, behaviourism cannot be the correct theory of mental states, Putnam concludes. However, functionalism avoids this objection because the ‘function’ of mental states is greater than just behaviour; my mental state of ‘pain’ could serve the function, alongside the behavioural output, of causing a belief that I am in pain, and a desire for it to stop. Even if this functional output has zero effect on my behaviour, it is a function of my mental state of pain. Functionalism avoids the issue of circularity which problematises behaviourism because it does not attribute mental states to particular behaviours, as proves to be the undoing of behaviourism.
Another way Putnam argues for the defensibility of functionalism is by proving how it overcomes a prevalent issue for type-identity theory — the issue of multiple realisability. Type-identity theory is the most obvious theory of mind for physicalists to defend, as it claims simply that all mental states are ontologically reducible — that they are the exact same referential object, or ‘thing’ — as brain states. Putnam would argue that the key feature of mental states, such as pain, is the function — as long as the mental state fulfils its role/function in the cognitive system, it can be experienced by a human, a silicon-based alien, or a shark — the defining characteristic of the mental state is simply the role it plays. The function of pain, which we might take to be an unpleasant sensation, giving rise to a desire for the sensation to stop, leading to the organism removing itself from the thing causing harm — is not specific to any physical set of behaviours, and anything that serves this function is ‘pain’, Putnam argues. Any computer, silicon alien, or animal with a system complex enough to produce this function would be able to feel pain, to have the mental state of ‘pain’, regardless of the physiological make-up of the brain in question — ‘pain’ is multiply realisable; it can be brought about by more than one ‘kind’ of physical brain structure. Type-identity theory does not allow this, as it gives a reductive analysis of mental states — that the mental state is identical (or ‘correlative’ in token identity theory, which is equally indefensible to this objection) to the brain state — and therefore could not allow for different physical ‘brains’ to feel the same mental state (even if the ‘brain’ in question can produce exactly the same set of functions in response to the painful stimuli). Functionalism avoids the multiple realisability objection which condemns type-identity theory, and Putnam considers functionalism to be the most defensible theory of mind for this reason.
These arguments demonstrate the benefits of subscribing to a functionalist theory of mind; perhaps why functionalism is the most familiar and received theory of mental states among philosophers of mind. However, the objections of inverted qualia, and the existence of qualia at all, contribute to the undoing of this seemingly tenable theory, and demonstrate that it does not provide a convincing account of mental states. The issue of inverted qualia is best demonstrated by the following argument, in which we assume that person 1 experiences grass as green in colour, and person 2 experiences the same grass in the colour that person 1 would call ‘red’, but to person 2 is also called ‘green’ :
P1. If functionalism is true, then two functionally identical mental states are the same mental state.
P2. The mental state of person 1 when observing green grass is functionally identical to person 2’s but is phenomenally different.
C1. Therefore, our two mental states are not the same mental state
C2. Therefore, functionalism is false.
This argument contends that there is clearly more to mental states than their function — if the function of the mental state, namely to identify that there is ‘green’ grass (and any accompanying behavioural or physiological changes) is consistent, yet the phenomenal experience (and thus the mental state) is contrasting, then functionalism cannot be providing the correct account of mental states. Patricia Churchland, proponent of ‘folk psychology’, argues that, in this case, the two mental states are not functionally identical — that there will be microscopic differences because of the complex causal relations of phenomenal properties with our brains — and therefore we have no reason to think it possible for inverted qualia of this kind to exist.
However, functionalism provides no evidence to verify this claim that there are microscopic functional differences at the relational phenomenal level (and thus that inverted qualia are impossible), and Block and Fodor point out the ‘conceptual coherence’ of the inversion — that even though we cannot know a priori that inverted qualia are possible, there is a ‘Cartesian intuition’ about the inversion which gives us evidence of its possibility. Given the lack of functionalist evidence that such inverted qualia are impossible, combined with our intuitive support for the idea, we can conclude that functionalism fails to adequately dispel the issue of inverted qualia, and gives an unconvincing account of mental states for this reason.
The crucial objection to Putnam’s functionalist theory of mental states is the existence of qualia — if phenomenal properties are the same thing as qualia, then they cannot be totally explained by functional roles, as they contain a relational property — a ‘what it is like’ to experience these mental states — which exists outside of its functional role:
P1. Qualia are intrinsic, non-Intentional aspects of our mental lives
P2. Intrinsic, non-Intentional properties cannot (by definition) by analysed sufficiently in terms of their causal roles, as they contain a relational property
C1. If qualia exist, some mental properties cannot be sufficiently analysed in terms of their causal roles
P3. Functionalism claims that all mental states, including phenomenal properties/qualia, can be sufficiently analysed in terms of their causal roles.
C2. If qualia exist, functionalism is false.
P4. Qualia exist
C3. Therefore, functionalism is false.
The physicalist in defence of functionalism must either borrow the argument of qualia eliminative materialists and claim that P4 is false, and qualia do not exist, or claim that qualia do not belong to the observer, and do not constitute part of the mental state. As neither of these responses are convincing — to claim that phenomenal properties of consciousness do not exist, we’d have to accept that there is nothing about a certain conscious experience which gives it a distinct experiential quality from any other, a tenet of qualia. Furthermore, to claim qualia do not belong to the observer seems incorrect, as how else might we explain the ‘introspective accessibility’ which constitutes a fundamental aspect of qualia as defined. As we have independent reasons to think both that qualia do exist, and certainly constitute part of the complete mental state, we must find Putnam’s functionalism to be inadequate in its effort to explain the totality of mental states.
Putnam’s functionalism is a more convincing theory than its physicalist alternatives — it explains multiple realisability where type-identity fails, and defeats circularity where behaviourism couldn’t. However, the undoing of functionalism is demonstrated by its incompatibility with inverted qualia, and reinforced by its friction with the relational aspect of qualia itself. Since the existence of qualia is (widely) accepted (and with good reason), functionalism cannot be regarded as a convincing account of mental states.
