[In the following essay, the reviewer finds Vaihinger's theory in The Philosophy of "As If" to be "indistinguishable from Pragmatism."]

In the slow crystallisation of the amorphous mass of thought which we label "Modern Realism," one of the most significant developments has been the reinterpretation of Kant. Hans Vaihinger has been the genius of this movement. To him more than to any other is due the credit of rescuing the philosophy of his great fellow-countryman from the gentle tyranny of his Hegelian paraphrasers. His keen and sympathetic understanding of English philosophy aided him in this work to no slight extent; as it helped to make him, in the years before the War, a far-sighted critic of his country's policy and a prophet of the disaster which has overtaken her. The translation into English of his greatest contribution to constructive thought—The Philosophy of "As If"—will find a warm welcome from all who have followed the tendencies of modern metaphysics.

The centre of gravity in Vaihinger's philosophy lies in an exuberant emphasis upon the constructive activity of the mind in all scientific procedure. His thesis has its source in those passages of the Critique of Pure Reason which stress the logical function of the imagination, the regulative Ideas of Reason, and the Antinomies. Kant had shown that our science can proceed only through the assumption of ideas which cannot be shown to be valid, because in the nature of the case they cannot be realised in experience. Vaihinger holds that these ideas can be shown to be false as well as necessary. With this in mind he proceeds to exemplify throughout the entire range of scientific, philosophic and religious thought the use of ideas which are not only false and necessary, but consciously so. The mathematician treats the circle as if it were a polygon with an indefinitely large number of sides, the physicist treats the heavenly bodies as if their mass were concentrated at a point; the biologist treats evolution as if it were purposive; the lawyer treats the adopted child as if it were a natural child. In these instances the scientific mind advances to the solution of its problems by a method of conscious fiction. It treats the unfamiliar as if it were an instance of the familiar, knowing all the while that it is not. Science is right in so doing, as is shown by the fact that most of its great modern triumphs have waited for their achievement upon the invention of just such fictional methods. To deny the mind's right to proceed in this way would be to wipe modern science entirely off the slate.

This is a summary statement of what we might call the "Special Theory" of the "As If." Logically, it succeeds in distinguishing a new type of judgment—the fictional—from the hypothetical with which it has hitherto been confused. A scientific hypothesis hopes to be true, and is scrapped whenever it is proved false: but a scientific fiction never claims to be true; it is used as an artifice, and the error which it involves is compensated in the final result by an antithetic error which cancels it out. Meta-physically, by means of the wide range from which the examples are chosen, and the lucidity with which they are classified and discussed, it vindicates brilliantly against many forms of realist theory, the presence of a constructive mental activity in the logical processes by which we attain knowledge.

But Vaihinger is not content with this important result. It is only the foundation of a General Theory which envelops the whole field of philosophy. The theory of fiction invades the whole domain of legitimate hypothesis and then proceeds to the conquest of the realm of ascertained truth. Not only does thought make use upon occasion of fictional artifices, it can make use of nothing else. Not only is the Atom a fiction, together with Matter and Personality, Free-will and the Differential Calculus, Force and the Deity; but the categories of thought are fictions, and also all our general ideas. Nothing remains standing before the ruthlessness of the attack, except only the observable regularity of the sequences of our sensations. The world of ideas as a whole is a tissue of fictions, an elaborate and essential falsehood.

The whole conceptual world is inserted between sensations; these alone are ultimately given.

The goal of all science, the reduction of all happenings to atomic movements in space, is in fact an attempt to reduce all existence to ideational constructs of a purely fictional nature.

Vaihinger is not blind to the general implications of such a philosophy. "Mankind," he tells us, "is beginning to realise to an increasing extent that understanding is only an illusion, that life and action are based upon illusions, and lead to illusions." Yet in spite of this he refuses to be called a sceptic. The theory sounds sceptical only because we are such incurable optimists and expect more than we can have.

The wish to understand the world is not only unrealisable, but also a very stupid wish.

We ought to be content with our illusions, because:

The Ideal, the Unreal, is the most valuable; men must demand the impossible even if it leads to contradictions.

After all, thought is not an end in itself, but an instrument for the service of life.

The actual purpose of thought is not thought itself, but behaviour and ultimately ethical behaviour.… We do not understand the world when we are pondering over its problems, but when we are doing the world's work.

The final result seems to be indistinguishable from Pragmatism. Vaihinger denies the identification, apparently because he refuses to say that a fruitful fiction is true because it works. Yet he maintains that we can no longer talk about truth at all, in the ordinary sense. "Truth is really merely the most expedient type of error." In other words, Truth itself is not truth but fiction, and the dispute with the Pragmatist is but a question of terminology. This is hidden behind the screen of "experience and intuition, which are higher than all human reason." In sensation and the regularities of sense-experience, we are at least face to face with reality and fact. Surely in this the great Kantian has forgotten his Kant. A "sensation" is as much a fiction as an "atom." And the perception of the regularities of sequence involves recognition and the categories. For how can I remember except by treating what is a present experience as if it were a past one? Thus if Vaihinger's General Theory is right, the whole field of experience, sensory and conceptual alike, is an as if that refers to nothing, a fiction created out of nothing, so far at least as it has any form. And, indeed, the General Theory makes the Special Theory meaningless, because it leaves no room for the essential distinction between "fiction," "hypothesis" and "fact."