I must not, however, press the parallel too far. Descartes did not, and could not, regard our beliefs as a developing system, which is not merely increasing by external accretion, like a crystal in its mother-liquid, but is growing and changing through and through like a living organism. Such conceptions were not of his age or country, nor, if they had been, could they have been easily accommodated to his peculiar genius. His was the mathematical temperament, always striving for precise definitions and rigorous proof; always tolerant of any simplification of the concrete complexities of reality, which would make them amenable to deductive treatment. Of this, as a method, we need make no complaint. Within due limits it is invaluable. But Descartes, so to speak, “objectified” it. He assumed that any judgment which could properly be described as “clear and distinct” was not only convenient in form, but true in substance. The world, alas! is not so made. The things which are clear and distinct are usually things of our own creation. Definitions, abstractions, diagrams, syllogisms, machines—such and such like are, or may be, “clear and distinct.” But the great facts which we have not made—these, at our present level of knowledge, are never clear and never distinct. Life, the organism, the self, the state, the world, freedom, causality, the flow of time, the relation between mind and body, between perceiver and perceived, between consciousness and sub-consciousness, between person and person (I say nothing of beauty, of virtue, or of God)—who is there will dare to say that he either finds in these notions, or can put into them without injury, the qualities which Descartes deemed the inevitable marks of real and certain knowledge? Truth, for us, is a plant of a different and of a slower growth. How much indeed of that growth consists in discovering that what we thought was clear is in fact obscure; what we thought was simple is in fact complex; what we thought was distinct is in fact confused; and how helpful are such discoveries to the augmentation of learning! However this may be, there is nothing in the doctrine of “congruity” which should shock those who are jealous for the supremacy of reason and the dignity of science. It is science itself which assures us that all premises, all conclusions, and all the logical links by which they are connected must be regarded as natural products. It is science itself which assures us that they belong, like all natural products, to the tissue of causes and effects whose lengthening web is continuously thrown off by the loom of time. It is science itself which requires us to harmonise these two aspects of the knowing process—the one logical and timeless; the other causal and successive.