a priori; a posteriori
These terms are best left to philosophical contexts. Very simply, a priori, the more common term, means “deductively; reasoning from the general to the particular,” and a posteriori means “inductively; reasoning from the particular to the general, or from known effects to their inferred causes.” Here a priori is used correctly, although the writer might better have written deductive—e.g.:
“Witherspoon's teaching is not limited to that particular inference; it counsels against any a priori judicial assumptions about the views of veniremen.”
Eric Schnapper, Taking Witherspoon Seriously, 62 Tex. L. Rev. 977, 993 (1984).
A priori becomes vague and confusing when it is used to mean “presumably” or “without detailed consideration,” as here:
“But we cannot say, a priori, without evidence, that there is not a sufficient rational distinction between such restaurants and other commercial establishments to warrant a study.”
Schafer v. City of New Orleans, 743 F.2d 1086, 1090 (5th Cir. 1984).
Nonlawyers sometimes misuse a priori for prima facie—e.g.:
“In short, there is a reasonably persuasive a priori [read prima facie] case at least for the proposition that the existence of liberal democracy in two powerful countries makes it very unlikely that they will resort to the threat of force in their mutual relations.”
Tom Farer, To Shape the Nation's Foreign Policy, Diogenes, 22 Sept. 2004, at 71.
“This creates an a priori [read a prima facie] case for regulation, and may also explain some of the failures that Brown and Jacobs record.”
Natalie Gold, Where Rhetoric Meets Reality, Times Higher Educ. Supp., 20 Nov. 2008, at 48.
Garner’s Dictionary of Legal Usage, Bryan A. Garner