progenitors, Hume and Leibniz.[21] III. GENERAL In indicating some of the main features of Kant’s general teaching, I shall limit myself to those points which seem most helpful in preliminary orientation, or which are necessary for guarding against the misunderstandings likely to result from the very radical changes in terminology and in outlook that have occurred in the hundred and thirty years since the publication of the _Critique_. Statements which thus attempt to present in outline, and in modern terms, the more general features of Kant’s philosophical teaching will doubtless seem to many of my readers dogmatic in form and highly questionable in content. They must stand or fall by the results obtained through detailed examination of Kant’s _ipsissima verba_. Such justification as I can give for them will be found in the body of the _Commentary_. I. THE NATURE OF THE _A PRIORI_ The fundamental presupposition upon which Kant’s argument rests--a presupposition never itself investigated but always assumed--is that universality and necessity cannot be reached by any process that is empirical in character. By way of this initial assumption Kant arrives at the conclusion that the _a priori_, the distinguishing characteristics of which are universality and necessity, is not given in sense but is imposed by the mind; or in other less ambiguous terms, is not part of the matter of experience but constitutes its form. The matter of experience is here taken as equivalent to sensation; while sensation, in turn, is regarded as being the non-relational. The explanation of Kant’s failure either to investigate or to prove this assumption has already been indicated. Leibniz proceeds upon the assumption of its truth no less confidently than Hume, and as Kant’s main task consisted in reconciling what he regarded as being the elements of truth in their opposed philosophies, he very naturally felt secure in rearing his system upon the one fundamental presupposition on which they were able to agree. It lay outside the field of controversy, and possessed for Kant, as it had possessed for Hume and for Leibniz, that authoritative and axiomatic character which an unchallenged preconception tends always to acquire.