Online research in philosophy

Hilary Putnam has famously argued that we can know that we are not brains in a vat because the hypothesis that we are is self-refuting.1 While Putnam’s argument has generated interest primarily as a novel response to skepticism, his original use of the brain in a vat scenario was meant to illustrate a point about the “mind/world relationship.”2 In particular, he intended it to be part of an argument against the coherence of metaphysical realism, and thus to be part of a defense of his conception of truth as idealized rational acceptability. Putnam’s argument has drawn a good deal of criticism already, but it will be argued here that these criticisms fail to capture the central problem with Putnam’s argument. Putnam’s conclusions about the self refuting character of the brain in a vat hypothesis, rather than simply being a consequence of his semantic externalism, will be shown to be actually out of line with central and plausible aspects of his own account of the relationship between our minds and the world. Reflections on intentionality and semantics ultimately give us no compelling reason to suppose that the beliefs expressed by claims like “I am a brain in a vat” could not be true,3 but (pace Putnam) this supports neither skepticism nor metaphysical realism.

In this paper I argue that Modal Realism, the thesis that there exist non-actual possible individuals and worlds, can be made compatible with Metaphysical Nihilism, the thesis that it is possible that nothing concrete exists. Modal Realism as developed by Lewis rules out the possibility of a world where nothing concrete exists and so conflicts with Metaphysical Nihilism. In the paper I argue that Modal Realism can be modified so as to be compatible with Metaphysical Nihilism. Such a modification makes Modal Realism neither incur further theoretical costs nor lose its theoretical benefits. Thus such a modification constitutes an improvement of Modal Realism.

In this paper I argue that the explanationist argument in favour of moral realism fails. According to this argument, the ability of putative moral properties to feature in good explanations provides strong evidence for, or entails, the metaphysical claims of moral realism. Some have rejected this argument by denying that moral explanations are ever good explanations. My criticism is different. I argue that even if we accept that moral explanations are (sometimes) good explanations the metaphysical claims of realism do not follow.

According to metaphysical realism, there may be features of reality which we cannot conceive. If this thesis of cognitive closure is inconsistent, then, pace dialetheism, metaphysical realism proves incoherent. Recently, Graham Priest has revived Berkeley's idealist argument meant to show that cognitive closure is inconsistent. If cogent, this argument poses a threat to metaphysical realism. I argue that while Priest's reconstruction of Berkeley's argument may be seen to be paradoxical on one interpretation of ‘conceive’, that interpretation is not the intended one. On the intended interpretation, the argument fails and hence leaves metaphysical realism unassailed.

Habermas's recent work in epistemology has been marked by a decisive rejection of his earlier epistemic conception of truth in which he understood truth as 'what may be accepted as rational under ideal conditions'. Arguing that no 'idealization of justificatory conditions' can do justice to both human fallibility and the unconditional nature of truth, he has attempted to develop a realistic conception of truth that severs any conceptual link between truth and justification while respecting the epistemic relevance of justification for ascertaining the truth. But realizing this second goal has proved elusive for Habermas because he veers too close to a form of metaphysical realism in his epistemology. By contrast, Hilary Putnam's recent turn to what he calls 'natural realism' is more successful in articulating a form of realism that, in taking its leave of an epistemic conception of truth, still manages to keep its distance from metaphysical realism.

In "Realism and Reason" Hilary Putnam has offered an apparently strong argument that the position of metaphysical realism provides an incoherent model of the relation of a correct scientific theory to the world. However, although Putnam's attack upon the notion of the "intended" interpretation of a scientific theory is sound, it is shown here that realism may be formulated in such a way that the realist need make no appeal to any "intended" interpretation of such a theory. Consequently, it can be shown that realism is immune to Putnam's criticism and that attempts at reformulating this criticism are not likely to meet with success.

Putnam originally developed his causal theory of meaning in order to support scientific realism and reject the notion of incommensurability. Later he gave up this position and adopted instead what he called ‘internal realism’, but apparently without changing his mind on topics related to his former philosophy of language. The question must arise whether internal realism, which actually is a species of antirealism, is compatible with the causal theory of meaning. In giving an answer I begin with an analysis of the content and metaphysical background of scientific realism. I show that it presupposes metaphysical realism and that Putnam's philosophical conversion is due to his becoming aware of the latter's incoherence. After giving a brief sketch of internal realism I conclude by arguing that within this new theoretical framework the causal theory of meaning loses its force as a weapon against incommensurability.

Two of Hilary Putnam's model-theoretic arguments against metaphysical realism are examined in detail. One of them is developed as an extension of a model-theoretic argument against mathematical realism based on considerations concerning the so-called Skolem-Paradox in set theory. This argument against mathematical realism is also treated explicitly. The article concentrates on the fine structure of the arguments because most commentators have concentrated on the major premisses of Putnam's argument and especially on his treatment of metaphysical realism. It is shown that the validity of Putnam's arguments is doubtful and that realists are by no means forced to accept the theses Putnam ascribes to them. It is concluded that Putnam fails to give convincing arguments for rejecting mathematical or metaphysical realism. Furthermore, Putnam's internal realism is discussed critically.

Hilary Putnam and Nelson Goodman are two of the twentieth century's most persuasive critics of metaphysical realism, however they disagree about the consequences of rejecting metaphysical realism. Goodman defended a view he called irrealism in which minds literally make worlds, and Putnam has sought to find a middle path between metaphysical realism and irrealism. I argue that Putnam's middle path turns out to be very elusive and defend a dichotomy between metaphysical realism and irrealism.

Horwich argues that we should reject metaphysical realism, but that we can preserve semantic realism by adhering to a redundancy theory of truth and a confirmationist account of linguistic understanding. But the latter will give us semantic realism only if it allows that the truth-values of sentences may transcend our recognitional capacities, and this is possible only insofar as we covertly reintroduce metaphysical realism. In spite of its intuitive appeal, we should not endorse semantic realism, but this need not bear upon the tenability of scientific realism.