FAITH AND REASON 355Ways of being falsified
A standard case of falsification is mistaken prediction; it notes that
theory T entails that result R will obtain if a certain experiment is
performed, the experiment is run, and R does not occur – so T is
falsified. What is crucial here is not that the false proposition that T
entails is future tense; what matters is that T entails a proposition and
we have discovered that the proposition is false. It is having discernible
entailments whose truth value is discoverable that matters here, and the
idea that this is always or essentially a matter of prediction is mistaken.
The false proposition entailed by a falsified theory need not be a
mistaken report of observational consequences. There are various
grounds on which a theory may be rationally rejected. For example,
there are various types of what we might call intellectual suicide. Here
are three. The claim No one can know anything said in English is self-
defeating in that (i) no one could know it were it true. The claim
Nothing said in English can be true is self-refuting in that (ii) its being
true is incompatible with what it says is true. Nothing can be said in
English is self-destroying, (iii) being an instance of what it says cannot
exist. A more interesting example of self-destruction is the claim All
language is metaphorical; as a nonmetaphorical use of language, it is
itself the very sort of thing it says there cannot be. There are deep
problems with such claims but the problems do not arise from their
entailing false observation statements. Such claims, and views to which
they are essential, commit intellectual suicide; there is no chance that
they constitute knowledge. A theory defective in any of these ways is
rationally rejected.^12
A theory that essentially contains a contradiction is false. (Theory T
contains proposition P essentially if and only if with P, T explains the
data it is intended to explain, and without P, it does not.) Any set of
propositions that is essentially incoherent cannot comprise a theory.
(Propositions P and Q are coherent if and only if they are (i) logically
consistent and (ii) mutually relevant to explaining what the theory in
which they both appear is intended to explain.) If it is essential to
theory T that propositions of kind K1 be translatable without remainder
into propositions of kind K2, and they cannot be, then T is false. If it is
essential to theory T that propositions of kind K1 not be translatable
without remainder into propositions of kind K2, and they can be, then T
is false. If theory T is such that if its truth conditions obtain, it is false,
then T is false whether or not its truth conditions obtain. (A theory’s
truth conditions are just what must exist for the theory to be true.) If
theory T is such that T is true entails T cannot be reasonably believed,