\A` pri*o"ri\ [L. a (ab) + prior former.]
1. (Logic) Characterizing that kind of reasoning which
   deduces consequences from definitions formed, or
   principles assumed, or which infers effects from causes
   previously known; deductive or deductively. The reverse of
   a posteriori.
3. (Philos.) Applied to knowledge and conceptions assumed, or
   presupposed, as prior to experience, in order to make
   experience rational or possible.
         A priori, that is, form these necessities of the
         mind or forms of thinking, which, though first
         revealed to us by experience, must yet have
         pre["e]xisted in order to make experience possible.
                                               --Coleridge.