Online research in philosophy

I am a realist of a metaphysical stripe. I believe in an immense realm of "modal" and "abstract" entities, of entities that are neither part of, nor stand in any causal relation to, the actual, concrete world. For starters: I believe in possible worlds and individuals; in propositions, properties, and relations (both abundantly and sparsely conceived); in mathematical objects and structures; and in sets (or classes) of whatever I believe in. Call these sorts of entity, and the reality they comprise, metaphysical. In contrast, call the actual, concrete entities, and the reality they comprise, physical. Physical and metaphysical reality together comprise all that there is. In this paper, it is not my aim to defend realism about any particular metaphysical sort of entity. Rather, I ask quite generally whether and how any brand of realism about metaphysical sorts of entity could be justified?

A well-known proof by Alonzo Church, first published in 1963 by Frederic Fitch, purports to show that all truths are knowable only if all truths are known. This is the Paradox of Knowability. If we take it, quite plausibly, that we are not omniscient, the proof appears to undermine metaphysical doctrines committed to the knowability of truth, such as semantic anti-realism. Since its rediscovery by Hart and McGinn ( 1976), many solutions to the paradox have been offered. In this article, we present a new proof to the effect that not all truths are knowable, which rests on different assumptions from those of the original argument published by Fitch. We highlight the general form of the knowability paradoxes, and argue that anti-realists who favour either an hierarchical or an intuitionistic approach to the Paradox of Knowability are confronted with a dilemma: they must either give up anti-realism or opt for a highly controversial interpretation of the principle that every truth is knowable.

This paper is concerned with the relationship between the metaphysical doctrine of realism about the external world and semantic realism, as characterised by Michael Dummett. I argue that Dummett's conception of the relationship is flawed, and that Crispin Wright's account of the relationship, although designed to avoid the problems which beset Dummett's, nevertheless fails for similar reasons. I then aim to show that despite the fact that Dummett and Wright both fail to give a plausible account of the relationship between semantic realism and the metaphysical doctrine of realism, the semantic issue and the metaphysical issue are importantly related. I outline the precise sense in which the evaluation of semantic realism is relevant to the evaluation of realism about the external world, a sense overlooked by opponents of Dummett, such as Simon Blackburn and Michael Devitt. I finish with some brief remarks on metaphysics, semantics, and the nature of philosophy, and suggest that Dummett's arguments against semantic realism can retain their relevance to metaphysical debate even if we reject Dummett's idea that the theory of meaning is thefoundation of all philosophy.

J.D. Collier sees Putnam as arguing (in the 'Brains in a Vat' chapter of [4]) that metaphysical realism is false.' He sees the argument as proceeding from the background assumption that metaphysical realism has the consequence that truth is 'radically non-epistemic', so that 'an [epistemically] ideal theory could be radically wrong about the world' [3, p. 413]. But, according to Collier, Putnam argues that 'an ideal theory satisfying all of our methodological and theoretical constraints cannot be false' [3, p. 413]. Collier attempts to defend metaphysical realism against this Putnamian attack by distinguishing 'between our ability to state a theory and our ability to conceive its possibility' [3, p. 413]. I will show that this defence is unsuccessful.

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.

What is real? Less than you might think. We advocate austere metaphysical realism—a form of metaphysical realism claiming that a correct ontological theory will repudiate numerous putative entities and properties that are posited in everyday thought and discourse, and also will even repudiate numerous putative objects and properties that are posited by well confirmed scientific theories. We have lately defended a specific version of austere metaphysical realism which asserts that there is really only one concrete particular, viz., the entire cosmos (see Horgan and Potrč (2000, 2002), Potrč (2003)). But there are various potential versions of the generic position we are here calling austere metaphysical realism; and it is the generic view that constitutes the ontological part of the overall approach to realism and truth that we will describe here.

When we think of scientific realism, there seem to be to ways to conceive of what it is about. The first is to see it as a view about scientific theories; the second is to see it as a view about the world. Some philosophers, most typically from Australia, think that the second way is the correct way. Scientific realism, they argue, is a metaphysical thesis: it asserts the reality of some types of entity, most typically, unobservable entities. I agree that scientific realism has a metaphysical dimension, but I have insisted that it has other dimensions too. In my (1999), I took scientific realism to consist of three theses (or stances).

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.

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.

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.