Albert Einstein on Metaphysics and Philosophy
Remarks on Bertrand Russell’s Theory of Knowledge
In the evolution of philosophical thought through the centuries the following question has played a major role: what knowledge is pure thought able to supply independently of sense perception? Is there any such knowledge? If not, what precisely is the relation between our knowledge and the raw material furnished by sense impressions?
There has been an increasing skepticism concerning every attempt by means of pure thought to learn something about the ‘objective world’, about the world of ‘things’ in contrast to the world of ‘concepts and ideas’. During philosophy’s childhood it was rather generally believed that it is possible to find everything which can be known by means of mere reflection. It was an illusion which anyone can easily understand if, for a moment, he dismisses what he has learned from later philosophy and from natural science; he will not be surprised to find that Plato ascribed a higher reality to ‘ideas’ than to empirically experienceable things. Even in Spinoza and as late as in Hegel this prejudice was the vitalising force which seems still to have played the major role.
The more aristocratic illusion concerning the unlimited penetrative power of thought has as its counterpart the more plebeian illusion of naive realism, according to which things ‘are’ as they are perceived by us through our senses. This illusion dominates the daily life of men and of animals; it is also the point of departure in all of the sciences, especially of the natural sciences.
As Russell wrote;
‘We all start from naive realism, i.e., the doctrine that things are what they seem. We think that grass is green, that stones are hard, and that snow is cold. But physics assures us that the greenness of grass, the hardness of stones, and the coldness of snow are not the greenness, hardness, and coldness that we know in our own experience, but something very different. The observer, when he seems to himself to be observing a stone, is really, if physics is to be believed, observing the effects of the stone upon himself.’
Gradually the conviction gained recognition that all knowledge about things is exclusively a working-over of the raw material furnished by the senses. Galileo and Hume first upheld this principle with full clarity and decisiveness. Hume saw that concepts which we must regard as essential, such as, for example, causal connection, cannot be gained from material given to us by the senses. This insight led him to a skeptical attitude as concerns knowledge of any kind.
Man has an intense desire for assured knowledge. That is why Hume’s clear message seemed crushing: the sensory raw material, the only source of our knowledge,through habit may lead us to belief and expectation but not to the knowledge and still less to the understanding of lawful relations.
Then Kant took the stage with an idea which, though certainly untenable in the form in which he put it, signified a step towards the solution of Hume’s dilemma: whatever in knowledge is of empirical origin is never certain. If, therefore, we have definitely assured knowledge,it must be grounded in reason itself. This is held to be the case, for example, in the propositions of geometry and the principles of causality.
These and certain other types of knowledge are, so to speak, a part of the implements of thinking and therefore do not previously have to be gained from sense data (i.e. they are a priori knowledge).
Today everyone knows, of course, that the mentioned concepts contain nothing of the certainty, of the inherent necessity, which Kant had attributed to them. The following, however, appears to me to be correct in Kant’s statement of the problem: in thinking we use with a certain right, concepts to which there is no access from the materials of sensory experience, if the situation is viewed from the logical point of view. As a matter of fact, I am convinced that even much more is to be asserted: the concepts which arise in our thought and in our linguistic expressions are all- when viewed logically- the free creations of thought which cannot inductively be gained from sense experiences. This is not so easily noticed only because we have the habit of combining certain concepts and conceptual relations (propositions) so definitely with certain sense experiences that we do not become conscious of the gulf- logically unbridgeable- which separates the world of sensory experiences from the world of concepts and propositions. Thus, for example, the series of integers is obviously an invention of the human mind, a self-created tool which simplifies the ordering of certain sensory experiences. But there is no way in which this concept could be made to grow, as it were, directly out of sense experiences.
As soon as one is at home in Hume’s critique one is easily led to believe that all those concepts and propositions which cannot be deduced from the sensory raw material are, on account of their ‘metaphysical’ character, to be removed from thinking. For all thought acquires material content only through its relationship with that sensory material. This latter proposition I take to be entirely true; but I hold the prescription for thinking which is grounded on this proposition to be false. For this claim- if only carried through consistently- absolutely excludes thinking of any kind as ‘metaphysical’.
In order that thinking might not degenerate into ‘metaphysics’, or into empty talk, it is only necessary that enough propositions of the conceptual system be firmly enough connected with sensory experiences and that the conceptual system, in view of its task of ordering and surveying sense experience, should show as much unity and parsimony as possible. Beyond that, however, the ‘system’ is (as regards logic) a free play with symbols according to (logically) arbitrarily given rules of the game. All this applies as much (and in the same manner) to the thinking in daily life as to the more consciously and systematically constructed thinking in the sciences.
By his clear critique Hume did not only advance philosophy in a decisive way but also- though through no fault of his- created a danger for philosophy in that, following his critique, a fateful ‘fear of metaphysics’ arose which has come to be a malady of contemporary empiricist philosophising; this malady is the counterpart to that earlier philosophising in the clouds, which thought it could neglect and dispense with what was given by the senses. … It finally turns out that one can, after all, not get along without metaphysics.
(Albert Einstein, Ideas and Opinions, 1944)
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