Kant defines analytic truth in terms of "conceptual containment". He also claims that there are some necessary truths which do not depend upon conceptual containments. These are synthetic a priori. If "true in virtue of conceptual containment" means "true solely in virtue of the concepts involved" or "true solely in virtue of the meaning of the terms involved", then many philosophers since Kant have argued that there can be no synthetic a priori. And there is some ground for concluding that this is what "true in virtue of conceptual containment" did in fact mean for Kant, since Kant insisted that all synthetic judgments are validated only by reference to some "third thing" over and above the concepts involved. The proper assessment of this issue requires a distinction between two theories of concepts, and two senses of conceptual containment. While in one sense there may be no truths which are necessary independently of conceptual containment, Kant has shown that in another sense there are such truths.