Commentary on JAMES R. HURFORD
Abstract: 96 words
Main Text: 963 words
References: 106 words
Total Text: 1165 words
Hurford's discussion also vindicates the Classical Empiricist program in semantics. The idea that PREDICATE(x) is the logical form of the sensory representations encoded via the dorsal and ventral streams validates empiricists' insistence on the psychological primacy of sense data, which have the same form. In addition to knowing the logical form of our primitive representations, however, we need accounts of (i) their contents and (ii) how more complex thoughts are derived from them. Ideally, our semantic vocabulary would both reflect the psychological 'primitiveness' of these representations and make clear how more complex representations derive from them.
Hurford presents himself as vindicating the semantic assumptions of logicians (as to the primacy of predication) and offering insights into the evolution of language (and particularly reference). However, it seems to me that this rich and thought provoking paper is equally well read as offering a partial resurrection and vindication of the Classical Empiricist program in philosophy of mind. Empiricists (such as the early Russell [1912, 1918], Wittgenstein [1922] and Carnap [1929, 1939] – or before them, Locke [1689], Berkeley [1710] and Hume [1740]) argued that all thoughts were in some way derived from 'sense impressions' or 'sense data,' that is, mental representations of the sensible properties of particular objects. While they differed as to how they expressed the contents of sense data in natural language ("This is red," 'There is a red thing," "Lo! a red thing," "Red here now"), it's pretty clear that what the empiricists had in mind when they talked of sense impressions or sense data were thoughts with precisely the logical form Hurford discusses: a sense datum was a thought to the effect that ($x)PREDICATE(x), where the variable x ranges over objects of sensation and the predicates represent sensible properties of those objects.
The empiricist program in philosophy of mind more or less died out in the 1950s, largely because empiricists made a big mistake about what to count as an 'object of sensation' or a 'sensible property of objects.' For largely non-empirical, epistemological reasons, they denied that sense data could represent physical objects and/or physical properties and thus hit the wall that ended their research program. A left turn would entail a descent into full-blown phenomenalism: if sense data can't represent physical objects and properties, then things in the world can't be physical objects with physical properties - this follows from the facts that (i) we clearly have thoughts about things in the world and (ii) all thoughts are derived from sense data. A right turn, on the other hand, led into a hideous maze of semantic dead ends. In the belief (or hope?) that our thoughts can indeed represent the objective and independent world about is, twentieth century theorists like Russell, the early Wittgenstein and Carnap attempted to show how higher-level representations of physical objects and their properties could be reduced to (or constructed out of) sensory primitives. This attempt, notoriously, was a failure and most philosophers now have abandoned any attempt to explain how our 'higher-level' thoughts about tables, dogs and quarks could be derived from the kinds of information that gets into our minds via our senses. Empiricism died a death, and Rationalism – the idea that there's stuff in our minds that doesn't come from the senses (I guess it must be innate!) – emerged as the dominant theoretical orientation throughout the cognitive sciences.
In arguing that what initially gets represented in the brain as a result of vision (and, perhaps, audition) is a thought of the form "THERE'S AN F!" Hurford is in effect arguing that the dead guys were right after all. First, sense data are, as one says, 'psychologically real' and do indeed play a central role in the aetiology of our thoughts. That is, the brain does represent the 'thereness' (or 'whereness') and 'whatness' of things, and it does so very early on in the process of thought formation. Secondly, the old guys were right in thinking that higher-order or more complex thoughts are derived from the primitive Hurfordian representations. Turning the Berkeleian argument on its head: we do have thoughts about independently-existing physical objects and these thoughts do derive from sense data (i.e., representations of the form ($x)PREDICATE(x)). So, while it's probably not true that thoughts about tables or cats are constructed out of or copies of sense data (as Carnap or Hume might have hoped), there must be a way to make an empiricist semantics work: the derivation of thoughts from sense data is 'psychologically real' as well.
Here, it seems to me, is where the real philosophical interest of Hurford's proposal lies. In order to pursue the empiricist program further, however, we need answers to two questions. First, what do the variables and predicates of PREDICATE(x) range over? Second, what are the processes of deriviation, abstraction, inference, binding (what to call them?) by which these initial representations are manipulated or transformed into the kinds of thoughts expressed by our propositional attitude ascriptions? Hurford has little of substance to say about the second question, but his survey of neuroscientific treatments of the first question is suggestive of the direction in which our semantics for thought needs to move. By making clear that the brain's most primitive predicates seem to carry both 'objective' information about objects' spatial location and physical features and 'subjective' egocentric or action-guiding information, Hurford's discussion in §4 indicates that their contents are almost certainly quite different both from those postulated by the Classical empiricists (RED etc.) and from those that are typically lexicalized in natural languages (BOX, LINE, CAT etc.). This suggests that it may have been a lack of an adequate theoretical vocabulary, more than anything else, that has hindered the empiricist semantic program! Classical empiricists misidentified the contents of sense data - and hence misconceived the nature of the 'derivation' process - because they sought to express the 'primitiveness' of sense data via 'primitive' natural language predicates ('Red' etc.). And because modern investigations into the semantics of thought (whether philosophical and neuroscientific) have had to use horribly complex agglomerates of natural and artificial linguistic forms to express the contents of our most primitive thoughts, they have been taken – wrongly – to be unEmpiricist in tenor. A new theoretical language for the semantics of thought is needed, one that more closely mirrors the language spoken by the brain. Hurford's paper is an important step in this direction.
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