Bill asked:

What is Anti-Realism? I have various friends who claim to be Anti-Realists, and all disagree with each
other. I have heard such expressions as 'Nothing is true unless it is known to be true' and 'there is no
mind-independant Reality' spoken as if they are self-evident, whereas I think they are (nearly)
self-evidently false. What is going on?

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Realists disagree with each other too. On the Realist view of personal identity defended by Chisholm,
in the thought experiment of human fission, there is a fact of the matter whether the person who
undergoes fission into physically and mentally indistinguishable individuals X and Y will 'be' individual
X or 'be' individual Y. Many philosophers who consider themselves 'Realist' would reject that solution
to the problem of personal identity, on the grounds that neither we, nor X or Y themselves, would be
able to tell who was the person who had survived, and who was a mere duplicate brought into
existence at the moment of fission.

Or consider the nature of time. Some Realists would find the hypothesis of an 'empty time' - a period
of time in which no events occur - acceptable, while others would find the hypothesis either
unacceptable, or acceptable only on the assumption that one could predict when such periods would
happen. Once again, the sticking point is the complete separation between the facts or the truth, and
possible knowledge.

'Nothing is true unless it is known to be true' is an extreme form of anti-Realism. I do not know of any
philosopher who holds that view. 'There is no mind-independent Reality' sounds like the immaterialist
philosophy of Berkeley, according to whom to be is 'to perceive, or be perceived'. What is striking
about Berkeley, however, is that the existence of God is an essential component of the theory. The
result is as Realist as you can get. Nothing has happened or will ever happen that God doesn't know
about. It's all down there in the blueprint or 'archetype' of the universe in God's mind.

What is anti-Realism? Anti-Realism concerns the nature of truth, rather than the nature of objects or
existence. Berkeley was a Realist about truth, but believed that 'material objects' were nothing more
than 'ideas'. In a series of articles, the Oxford philosopher Michael Dummett argues that verification
rather than truth should be the central concept of a theory of meaning that would account for our
understanding of the words which we speak. In learning a language, we are exposed to examples of
when the obtaining of such-and-such a state of affairs is verified. We readily generalise from this
knowledge to notions of 'what it would be' for a given proposition to be true, even though the
proposition in question may be unverifiable. But these imaginings have no explanatory function. In
Wittgenstein's words, they are like 'wheels that turn, even though no part of the mechanism turns with
it'.

Dummett's central claim is that the law of excluded middle, valid on a classical interpretation of logic,
cannot be justified by a verification conditions theory of meaning. I suspect he is wrong about this. My
own challenge to the Realist would be much more simple and direct. Consider any meaningful
proposition for which verification is clearly and unequivocally ruled out. (That's not difficult, there are
billions, most of them very uninteresting.) Call it P. Now, the Realist wants to tell me something very
important about P. What is it? Is P true? No, of course not. What the Realist wants to say is that P
'has' a truth value. What does that mean? To say that P is 'either true or false' is not to say anything
at all. But what more can one add? In searching for more, you will find yourself going round in circles.
Is that an adequate argument for Anti-Realism? - I don't know. Perhaps we are wrong in thinking that
one needs to 'say' something more here.

Geoffrey Klempner