sentence, and if we have understood it we have understood it as a tautology and know that it is true. For recognising something as tautological and recognising it to be true (by virtue of its form) are only two modes of expressing one and the same thing. The result is that perhaps some philosopher like Heraclitus' disciple Kratylus may doubt that we can ever be in possession of meaningful sentences, but he cannot even indicate by a motion of his sceptical finger that a person might understand a tautological proposition and not be convinced of its truth.
It is the fate of many post-Kantian systems of philosophy that in their endeavour to correct Kant by out-doing him they contradict him most decidedly in those particular places where he happened to be on the right track. Thus it is one of the basic doctrines of the most influential school of philosophy in contemporary Germany that Kant's opinion concerning the formal character of all a priori propositions was a mere prejudice. It is the so-called "phaenomenological" philosophy, founded by Husserl, that claims to be in possession of a great deal of a priori knowledge dealing with the very material or content of cognition, and not being due to any formal properties of the cognitive process. The followers of Husserl maintain with him that the source and justification of these indubitably and absolutely valid synthetic propositions is to be found in some kind of intuition called "Wesensschau", which is supposed to be the intuition not of an individual, singular thing, or event, but of the general nature, the "essence" of an entity or a class of entities.
They say, for instance, that such material, a priori synthetic knowledge is expressed by propositions like the following: "every musical tone must have a pitch and an intensity"; the surface of a physical body (or a patch on the visual field) cannot be both red and green at the same place and at the same time"; "orange as a colour quality ranges between red and yellow" and so forth. Husserl and his disciples believe that propositions of this sort form an unlimited field of important necessary truths which constitutes the proper domain of philosophy. Here at last, according to their opinion, it has become a strict science, as rich and as reliable mathematics.
The sober critic will have very grave doubts when he reads these statements, and two important points will force themselves upon his attention from the very beginning. In the first place, he will be astonished to see that the
