Functionalism

6. Absent qualia

The inverted spectrum thought experiment is consistent with the idea that appropriate functional organization guarantees conscious states of some kind. The only issue raised by the inverted spectrum argument is whether functional identity suffices to fix the qualitative identity of those conscious states. A more radical form of argument asks whether functional organization can guarantee consciousness at all. Are there not always going to be systems that display the appropriate functional organization yet lack qualia altogether?

Clearly, answers to this question will depend crucially on what qualifies as ‘appropriate functional organization’. Recall that earlier the notion of a functional role was introduced via Ramsey’s strategy for defining unobservable terms in terms of a theory. On this conception, you have mental states with a certain functional role if you have a set of states which interact in the way specified by some psychological theory T(M₁…M_n, O).

A number of thought experiments aim to show that any such notion of functional role must yield too ‘liberal’ an account of qualitative states, in that it will imply the presence of qualia in systems that in fact lack them. Imagine that the sensory messages into your brain and the motor messages going out are disconnected from your brain and instead linked by radio to a complicated structure made of old beer cans. This system of beers cans is arranged in such a way that its properties relate to each other and to your sensory and motor messages in just the way that psychological theory T says your brain states did before they were disconnected. Then the system consisting of your debrained body plus beer cans will have exactly the same functional organization as you had before your brain was disconnected. Yet it seems implausible that this system would be conscious, that there is something that it would be like to be a debrained body plus beer cans.

Even so, a significant number of functionalist philosophers are prepared to bite this bullet, and maintain that the beer can system would be conscious. After all, if some diseased part of your brain were replaced by some microscopic silicon-based circuitry, this would not necessarily stop you being conscious. What is the difference in principle, it could be asked, between this and the beer can case?

The beer can thought experiment starts with a normal human being, and then assumes the alteration of this human being’s brain. But there are further arguments which query whether even behavioural similarity to human beings is necessary for the relevant kind of functional organization. These arguments focus on the contribution of the observational terms O to the specification of functional roles. Note that it is essential to any plausible functionalism that these terms somehow be independently understood. For, if the O terms are themselves defined in terms of theory T, there will be far too many systems the properties of which satisfy T. Indeed, given a completely uninterpreted theory T(M₁…M_n, O), it is arguable that any physical system – the air molecules in your house, say – will display some set of properties that are related to each other as T says the Ms and O are related. So some prior understanding of the O terms is needed to give us any chance of ensuring that only conscious systems have the functional organization specified by T.

The natural way to do this is to equate O terms with terms for perceptual inputs (for example, ‘receiving visual stimuli from an ice cream’) and behavioural outputs (for example ‘moving your arm towards an ice cream’). But this, then, has the disadvantage of implying that some presumably conscious human beings, such as experimental subjects whose optic nerves are being stimulated by brain scientists, or paralyzed people who display no behavioural outputs, will lack the relevant functional organization.

The natural response to this difficulty (for a scientific functionalist at least, even if not for a common-sense functionalist) is to appeal to physiology to specify less peripheral inputs (kinds of stimulation of the optic nerve, say) and less peripheral outputs (kinds of activity in the motor cortex). But this physiological move threatens chauvinism. For it will exclude from the category of conscious beings any extraterrestrials and animals whose non-human physiologies do not include optic nerves and motor cortexes.

There remains some room for functionalists to manoeuvre here. One possibility would be to return to Lewis’ mixed theory, which would imply that the experimental subject and the paralyzed person are conscious because they are in the states that play the requisite causal role in their normal conspecifics, even if not in themselves. Another increasingly popular response is to appeal to teleological considerations, and understand ‘functional organization’ as not only specifying a causal structure but requiring in addition that this structure be a product of biological design. By appealing to this further sense of ‘function’, such ‘teleofunctionalists’ can specify that beings with different physiologies can nevertheless share the same functional organization, in virtue of having causally similar structures which have been designed for similar biological purposes.