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Hilary Putnam on Realism, Truth & Reason
Putnam is one of today’s leading living philosophers. He has changed his ideas repeatedly on some central philosophical problems including the nature of truth. Christopher Norris tells the story so far.
Hilary Putnam (born 1926) is a Harvard-based philosopher whose work has ranged widely over topics in metaphysics, epistemology, cognitive psychology, philosophy of science, language, logic and mathematics. Just recently he has extended his scope yet further into ethics, politics and religion, as well as certain regions where most of his colleagues would fear or disdain to tread, like literary theory and so-called ‘continental’ (post-war mainland-European) philosophy. Indeed Putnam stands out for this exceptional catholicity of interests at a time when so much philosophical work in the English-speaking world has become highly focused on matters of narrowly technical concern.
Putnam is also unusual in his willingness to constantly revisit his own earlier arguments and – very often – to come up with misgivings or objections which he takes to require a more-or-less drastic change of approach. This tendency can perhaps be traced back to his formative years in the late 1940s and early 50s, when Putnam was greatly influenced by the doctrines of the Logical Positivists, especially through the work of Rudolf Carnap. He has never renounced their basic methodological precept, which is that philosophers had better keep up with developments in the physical sciences and take them into account when advancing their own agenda. However, that programme was soon exposed to powerful counter-arguments, among them a wholesale demolition-job by Putnam's senior colleague at Harvard, W.V. Quine. Quine rejected the very idea – fundamental to Logical Positivism – of a clear-cut distinction between logical ‘truths of reason’ and empirical ‘matters of fact’. So Putnam had cause, early on, to cultivate the habit of critically examining his own preconceptions and where necessary revising or even renouncing them.
Strong Realism and Twin-Earth
The best-known example of this is the sequence of changes in Putnam's outlook as regards scientific realism; that is, the question of whether or not the world, together with its various objects, properties, structures and causes, objectively exists, independent of our minds and our senses. Some of Putnam's earliest (and still most influential) essays defended just such a ‘strong realist’ view. They did so, moreover, with the aid of arguments from philosophy of language and logic. The latter had to do with concepts of necessity and possibility; for instance, it is a necessary truth in our physical world and all other worlds physically like ours that water should possess the molecular structure H2O or gold the atomic number 79. Putnam used this in his famous Twin-Earth thought-experiment. We are asked to imagine that a space-traveller from Earth lands on the planet Twin-Earth and happily exclaims “Lots of water around here!” Putnam said our intrepid explorer would be right if all that watery-looking stuff was indeed H2O but wrong if it merely happened to look, taste and otherwise behave just like water, but actually had the molecular constitution XYZ. And of course an explorer from Twin-Earth would likewise be wrong if she looked around on Earth, uttered the same words, and thereby confused our water with the stuff – XYZ – so abundant back home.
Putnam rings some ingenious changes on this theme so as to bring out his realist point that ‘meanings ain’t just in the head’. In other words, what fixes the reference of natural-kind terms like ‘water’ and hence the truth or falsity of statements containing them is not the sense of this or that expression as conceived by this or that speaker but rather their picking out (or failing to pick out) objects or substances of just the specified kind. Thus the early Putnam adopted what is called an externalist position on issues of meaning and truth, as opposed to the hitherto dominant internalist view that sees knowledge as some epistemic state (such as ‘justified true belief’) enjoyed by certain well-placed or reliably informed individuals. This he took to have significant implications for philosophy of science and for the question of what constitutes the truth or falsehood of scientific theories. With respect to physical properties like molecular or subatomic structure, it is a matter of a posteriori necessity that ‘water = H2O’. In other words, it is a truth which had to be discovered through some process of empirical investigation but which none the less holds necessarily if that investigation was on the right track. However this applies only to worlds – such as our own – where water is indeed H2O and where no other substance can lay proper, scientifically-warranted claim to that title. The case is quite different with a priori truths – like those of logic or mathematics – which apply across all possible worlds and which therefore aren't subject to empirical testing. However, as concerns the physical sciences, this realist account bids fair to capture our best intuitions with regard to the growth of scientific knowledge and the need to explain how past theories – even those that have now been superseded – may yet have been ‘truth-tracking’ or ‘sensitive to future discovery’. Thus ‘water’ referred to H2O even when nobody had the least idea about its molecular constitution, just as ‘gold’ properly referred to gold even when nobody knew about atomic numbers and descriptions centred instead on attributes like ‘yellow’, ‘ductile’, or (at a later stage of scientific advance) ‘soluble in dilute nitric acid’. Indeed it referred to the same sort of stuff – the identical natural kind – even back at the time when ‘expert' opinion tended to confuse gold with iron pyrites (‘fool’s gold’) on account of the latter’s superficially similar appearance. What made “this is gold” a true or false statement – then as now – was whether or not the sample in question was actually (in virtue of its atomic constitution) a sample of just that kind.
The Retreat to Internal Realism
Putnam has since backed away from this ‘strong realist’ position under pressure of various (as he thinks them) decisive counter-arguments. The first clearly-marked stage in this retreat was his adoption of an ‘internal realist’ approach, according to which we could still quite properly talk of ‘truth’ but only in relation to a particular conceptual scheme or set of investigative interests and priorities. For he now took the view – influenced by Quine and other sceptically-minded thinkers – that his earlier ‘metaphysical’ (objectivist) realism placed truth beyond the utmost reach of humanly-attainable knowledge. Much better, Putnam thought, to give up that inherently self-defeating and scepticism-inducing idea in favour of a conception of knowledge as being framework-relative and an idea of truth – or, more aptly, of veridical warrant – that brought it back within the scope of what could be achieved. Such an outlook could be saved from wholesale relativism by invoking some limit-point notion such as ‘idealised rational acceptability’, truth ‘at the end of enquiry’, or that upon which our investigations are destined to converge when all the evidence has been gathered and evaluated under optimal conditions. This now seemed to Putnam the only hope of heading off the kinds of epistemological doubt that have plagued philosophers ever since Descartes. Otherwise there will always be room for the opponent to insert his sceptical wedge and remark that we can either have objective (recognition-transcendent) truth or knowledge within the bounds of present-best human cognitive grasp but surely not both. In which case, Putnam concluded, some middle-way solution along internal-realist lines is the best that we can reasonably hope for by way of meeting the sceptic's perennial challenge.
There were various reasons for Putnam's retreat to this compromise stance with regard to both the physical and the formal sciences, i.e. logic and mathematics. Among them were the well-known problems faced by any realist interpretation of quantum mechanics and the difficulty of defending synthetic a priori truth-claims in the wake of developments such as non-Euclidean geometry and General Relativity. Also there were the paradoxes of classical set theory as revealed by Russell and others, along with the proof by Gödel that formal proof procedures were insufficient to establish the validity even of first-order logic or elementary arithmetic. Above all, the realist about ‘natural kinds’ – like Putnam in his own earlier writings – had a problem explaining how such kinds could be taken to exist as a matter of real-world, objective fact quite apart from our various interest-specific interpretations. For instance, they would have to say that a term such as ‘jade' had no proper application since it conflated the two quite distinct natural kinds jadeite and nephrite, or that various traditional species-attributions as regards plants and animals were illicit since they lacked any reputable basis in the latest genetic research. This seems to go against a more common sense idea of realism. Thus rather than ‘cutting nature at the joints’ (in Plato’s rather gruesome metaphor) such categories should instead be seen for what they are: different framework-relative modes of classification which pick out just those features which count as salient for some particular descriptive purpose. This is still realism, Putnam contends, but a realism shorn of unnecessary ‘metaphysical’ accretions and thus restored to the compass of humanly-attainable epistemic grasp.
Putnam Goes Pragmatist
Opinions differ as to whether this ‘internal realist’ approach manages to head off the sceptical challenge while retaining its realist credentials or whether it is just a kind of figleaf realism, that is to say, an anti-realist (or paradigm-relativist) theory that dare not quite speak its name. More recently, responding to criticisms on the latter score, Putnam has proposed various alternative formulations of his middle-ground epistemological stance. In short, he has moved from a ‘naturalised’ epistemology – though one that allows more room for normative values of truth and rationality than find any place in Quine's radically empiricist approach – to a pragmatist standpoint which sees truth as ‘what’s best in the way of belief’.
At the same time he has also shifted ground on issues in cognitive psychology, from the functionalist position that mental processes can be described entirely in terms of computations on various (physical but not necessarily organic, perhaps silicon-based) sorts of ‘hardware’ to an approach that gives far less weight to such ultimately science-led explanations. Here again there is much debate as to just how far Putnam has gone in a hermeneutic or ‘strong’ descriptivist direction, that is, toward an outlook squarely opposed to any form of scientific or philosophical realism. The issue is sharpened by his growing willingness to take on board certain arguments from so-called ‘continental’ philosophy, even though that tradition of thought has always been seen by its Anglophone ‘analytic’ opponents as deplorably prone to unscientific and (as they would have it) unphilosophical vagaries. Still it should be clear to any reader of Putnam's later work that his leanings toward anti-realism have always been to some extent tempered by a sense of the need for philosophers to square their views with current thinking in the physical sciences. Hence his keen awareness, which I've already mentioned, of the problems thrown up by developments such as non-Euclidean geometry, quantum mechanics, and Gödel's incompleteness theorem. If Putnam's response to these problems will most likely strike the realist as moving too far in the opposite (anti-realist or framework-relativist) direction, it is none the less argued with great vigour and with a finely-judged sense of the opposing considerations.
This quality is also characteristic of his recent attempts to defuse the quarrel between ‘analytic’ and ‘continental’ philosophy by persuading both parties to recognise the extent of shared ground between them, without glossing over their very real differences of interest and priority. On the standard (analytically received) view the former is devoted to a quest for constructive solutions to well-defined philosophical problems while the latter adopts some version of the hermeneutic claim that interpretation goes ‘all the way down’, i.e., that such issues can only be addressed through a sensitive awareness of the cultural and historical contexts within which they have arisen. Putnam's effort to bridge this divide is partly the result of his increasing sense of the need to break down such entrenched oppositions as those between fact and value or between the kinds of approach deemed valid in the natural sciences and the kinds of ethically-responsive approach that are taken to characterise the social sciences and humanities. Hence – among other moves in this direction – his argument against the narrowly positivist idea of objectivity or value-neutrality in fields like economics, where there is always some appeal to various, often sharply conflicting, notions of the human good. Here again one can see the continuity of Putnam's interests over the past five decades despite all his openly-acknowledged changes of mind on some basic issues. He is still much concerned with the problems thrown up by logical empiricism, not only on its homeground of epistemology and philosophy of science but also in those areas – ethics and politics among them – where the imposed divorce between factual and evaluative statements has wrought such widespread damage.
As I have said, it is quite possible to welcome this aspect of Putnam's work without accepting his view that it entails an abandonment of the causal-realist approach via inference to the best (most rational) explanation that typified his early writings. Indeed the chief virtue of that approach was that, unlike the hard-line positivist doctrine, it found room for both a sturdily realist conception of scientific truth and an acceptance of other modes of discourse with their own distinctive standards of truth and rationality. At times there is the feeling that Putnam has been driven – perhaps against his better wisdom – to enlist on the anti-realist side in various current disputes and hence to put at risk some of his most important bridge-building endeavours. For instance, one could argue that Putnam's later scepticism about a priori truths in the formal sciences and natural-kind talk in physics or biology results from his extreme sensitivity to the sorts of hyperbolic doubt raised by thinkers who often arrive at them (ironically enough) on a priori grounds and have nothing like his detailed grasp of the substantive scientific issues. This applies especially to those passages in his later books where Putnam adduces a range of conceptual problems in philosophy of science, logic and mathematics and takes them to entail either a radically sceptical conclusion or else – his preferred outcome – the retreat to some scaled-down (whether framework-relative, naturalised, or pragmatist) version of ‘realism’. All the same, what has typified Putnam's work throughout an immensely distinguished and productive philosophical career is his effort to see all around these issues and his constant readiness to re-think them in response to various counter-arguments, whether of his own or of others' devising.
© C. Norris 2004
Christopher Norris is Professor of Philosophy at Cardiff University.
Some books by Hilary Putnam
Mind, Language and Reality (Cambridge University Press, 1975)
Mathematics, Matter and Method (Cambridge U.P., 1975)
Meaning and the Moral Sciences (Routledge & Kegan Paul, 1978)
Reason, Truth and History (Cambridge U.P., 1981)
Realism and Reason (Cambridge U.P., 1983)
Pragmatism: an open question (Blackwell, 1995)
The Many Faces of Realism (Open Court, 1987)
Representation and Reality (Cambridge U.P., 1988)
Realism With a Human Face (Harvard University Press, 1990)
Renewing Philosophy, ed. James Conant (Harvard U.P., 1992)
Words and Life, ed. Conant (Harvard U.P., 1994)
The Threefold Cord: mind, body, and world (Columbia U..P, 1999)
The Collapse of the Fact/Value Dichotomy, and Other Essays (Harvard U.P., 2003)