Language, Truth and Logic by A.J. Ayer

Author:A.J. Ayer
Language: eng
Format: epub
Publisher: Penguin Books Ltd
Published: 2001-11-15T00:00:00+00:00

CHAPTER 7

THE SELF AND THE COMMON WORLD

IT is customary for the authors of epistemological treatises to assume that our empirical knowledge must have a basis of certainty, and that there must therefore be objects whose existence is logically indubitable. And they believe, for the most part, that it is their business, not merely to describe these objects, which they regard as being immediately ‘given’ to us, but also to provide a logical proof of the existence of objects which are not so ‘given’. For they think that without such a proof the greater part of our so-called empirical knowledge will lack the certification which it logically requires.

To those who have followed the argument of this book it will, however, be clear that these familiar assumptions are mistaken. For we have seen that our claims to empirical knowledge are not susceptible of a logical, but only of a pragmatic, justification. It is futile, and therefore illegitimate, to demand an a priori proof of the existence of objects which are not immediately ‘given’. For, unless they are metaphysical objects, the occurrence of certain sense-experiences will itself constitute the only proof of their existence which is requisite or obtainable; and the question whether the appropriate sense-experiences do or do not occur in the relevant circumstances is one that must be decided in actual practice, and not by any a priori argumentation. We have already applied these considerations to the so-called problem of perception, and we shall shortly be applying them also to the traditional ‘problems’ of our knowledge of our own existence, and of the existence of other people. In the case of the problem of perception, we found that in order to avoid metaphysics we were obliged to adopt a phenomenalist standpoint, and we shall find that the same treatment must be accorded to the other problems to which we have just now referred.

We have seen, furthermore, that there are no objects whose existence is indubitable. For, since existence is not a predicate, to assert that an object exists is always to assert a synthetic proposition; and it has been shown that no synthetic propositions are logically sacrosanct. All of them, including the propositions which describe the content of our sensations, are hypotheses which, however great their probability, we may eventually find it expedient to abandon. And this means that our empirical knowledge cannot have a basis of logical certainty. It follows, indeed, from the definition of a synthetic proposition that it cannot be either proved or disproved by formal logic. The man who denies such a proposition may be acting irrationally, by contemporary standards of rationality, but he is not necessarily contradicting himself. And we know that the only propositions that are certain are those which cannot be denied without self-contradiction, inasmuch as they are tautologies.

It must not be thought that in denying that our empirical knowledge has a basis of certainty we are denying that any objects are really ‘given’. For to say that an object is immediately ‘given’ is

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