Putnam's natural realism and the question of a perceptual interface

Abstract

According to Hilary Putnam, natural realism is a form of direct realism in the philosophy of perception that promises to help see us past an irresolvable metaphysical dispute between realism and anti-realism. Illumination depends upon the claim that in perception that there is no interface between the cognitive powers of the mind and the causal powers of the world. In the present paper I aim to show that there is a hidden complexity in Putnam's notion of a perceptual interface. On a trivializing reading, Putnam intends only to reject a modern materialist version of the traditional ‘veil of ideas’. On a richer reading, he intends also to reject the view that the intentional content of experience is autonomous with respect to the external world. I conclude by suggesting that natural realism is not mere common sense and that its fate is tied to its ability to respond to the skeptical threats that help to motivate the traditional options of realism and antirealism.

Notes

The Dewey Lectures, titled ‘Sense, Nonsense and the Senses: An Inquiry into the Powers of the Human Mind’, originally appeared in the Journal of Philosophy (Vol. 91, 1994). They are reprinted in Putnam (1999) and all references will be to this text unless otherwise indicated.

Note that Putnam (1981, 49) misleadingly speaks of truth as ‘some sort of (idealized) rational acceptibility’. What ‘ideal’ means is simply ‘good enough’. See Putnam (1992, 403, cf. n.17).

Putnam (1992, 371) has written that ‘natural realist accounts are distinguished by their rejection of the very idea of “sense data”’.

This expression is borrowed from John McDowell (1982).

In making this reply, no attempt is made to offer an explanation of the fact that deceptive and non-deceptive perception can be phenomenally indistinguishable.

It is also fair to complain that one ought not to assume that the same notion of ‘inference’ is applicable both to our thinking and to a sub-personal account of the underlying mechanisms responsible for it.

See Putnam (2002) for reservations about McDowell's fully conceptualized conception of experience.

In a discussion of the decline of sense-data theories in 20th-century philosophy, Tim Crane (1992, 5) remarks ‘that in a set of essays devoted to perception published twenty years ago, F. Sibley's Perception: A Symposium (1971), there was hardly a mention of sense-data’.

See, for example, Grice (1988) and Strawson (1974, 1988).

The fact that subjective experiences are effects of outer objects does not imply, though it may encourage, the view that these effects are the immediate objects of perceptual awareness. Strawson, a causal theorist, writes: ‘mature sensible experience (in general) presents itself as, in the Kantian phrase, an immediate consciousness of the existence of the things outside us’ (1988, 96).

Of course, in this case, we could say that the intentional object of the experience does not exist. For a defence of the insubstantial view of intentional objects that I am advocating, see Crane (2001).

The interchangeability of the terms ‘sense-data’ and ‘experience’ appears to confirm that all that is at issue is a ‘veil-of-ideas’ theory of perception plus a ‘simple linguistic reform’.

This description certainly seems to characterize accurately those philosophers who believe that secondary qualities such as colour are to be understood in terms of the dispositions of objects to produce colour qualia in the mind.

Putnam (1975) originally formulated this externalist position only with respect to the meanings of natural terms such as ‘water’, ‘aluminium’ and ‘elm trees’; and, by implication, those mental states whose content involves reference to such terms. There is a question about how far this account can be extended to other mental states. See Burge (1982).

Strawson (1985) follows Searle in advocating just such an internalist conception of the intentional content of experience. See also McGinn (1982, 38). However, defenders of irreducible qualia are the current orthodoxy. See, for example, Jackson (1982), Peacocke (1983) and Shoemaker (1996).

The intuitive pull of this idea may, but need not, depend upon the idea that the content of experience is non-conceptual.

For some subjective experience may only refer to qualia, for others who deny the existence of qualia, it may refer only to intentional content, and, of course, for others still it may include both kinds of content.

Cf. Haugeland (1998).

For a detailed defence of this conception of content, see McDowell (1986).

The importance of perceptually demonstrative thought is largely implicit in Putnam's writing but is more evident in McDowell (e.g. 1986). For an argument to the effect that direct realism can be understood solely in terms of demonstrative singling out, see Snowdon (1992).

It is this object-dependence of the content of non-deceptive sense experience that, I take it, Putnam is indicating by way of the italicized terms in the expressions: (i) ‘sensing of aspects of the reality “out there” ’ (10) and (ii) ‘“external” things, cabbages and kings, can be experienced’ (20).

Putnam remarks: ‘If one wants to describe the use of the sentence “There is a coffee table in front of me,” one has to take for granted its internal relations to, among others, facts such as that one perceives coffee tables … I mean the full achievement sense, the sense in which to see a coffee table is to see that it is a coffee table that is in front of one’ (14).

There are important differences between long-term and recent envatment which bear on the question of the content of the brain's psychological attitudes and experiences. The intelligibility of recent envatment—a condition that ensures that the reference of one's terms and concepts systematically fails—is all that I need rely on in the present context. Also note that in brain-in-a-vat scenarios we must distinguish the material objects that are apparently experienced from the material objects that actually exist, for example, the vat of nutrients, the super-computer, the super-scientist.

Here it is worth recalling Wittgenstein (1972, 58): ‘There is no common sense answer to a philosophical problem’.