The term _pure_ (_rein_) thus acquires a second meaning distinct from that defined above.[220] It is no longer employed as identical with _a priori_, but as a subdivision of it, meaning _unmixed_. Its opposite is no longer the empirical, but the impure or mixed. Owing, however, to the fact that “pure” (in its first meaning) is identical with the _a priori_, it shares in all the different connotations of the latter, and accordingly is also employed to denote that which is _not relative_. But “pure” has yet another meaning peculiar to itself. The phrase “independent of experience” has in reference to “pure” an ambiguity from which it does not suffer in its connection with “_a priori_” (since mathematical knowledge, whether pure or applied, is always regarded by Kant as _a priori_). It may signify either independence as regards _content and validity_, or independence as regards _scope_. The latter meaning is narrower than the former. By the former meaning it denotes that which originates, and can possess truth, independently of experience. By the latter it signifies that which is not only independent of sense but also applies to the non-sensuous. In this latter meaning pure knowledge therefore signifies transcendent knowledge. Its opposite is the immanent. The various meanings of “pure” (four in number) may be tabulated as follows: (_a_) (1) _A priori_: independent of experience as regards origin and validity. (Its opposite = empirical.) { (2) Absolutely independent of experience. (Its { opposite = relative.) { (3) Unmixed with experience. (Its opposite = { impure or mixed.) (_b_) (4) Independent of experience as regards scope = transcendent. (Its opposite = immanent.) All these varied meanings contribute to the ambiguity of the title of the _Critique_. Kant himself employs the title in all of the following senses: 1. Critique of absolutely pure _a priori_ knowledge, determination of its sources, conditions, scope and limits. 2. Critique of all _a priori_ knowledge, relative as well as absolute, in so far as it depends upon _a priori_ principles, determination, etc. 3. Critique of all knowledge, whether _a priori_ or empirical, determination, etc. 4. Critique of transcendent knowledge, its sources and limits.