a priori

1. 1
   adjective

   Reasoned out from theory and hypothesis, without depending on experiment or other empirical evidence.

   Philosophers still argue over whether the truths of arithmetic count as a priori knowledge.

   The economist rejected the policy on a priori grounds, before any data from the pilot program had come in.

   Similartheoretical, deductive

   Oppositeempirical, experiential

   Note

   The logician's sense, closest to the Latin: Medieval Latin ā priōrī, literally "from the former," named reasoning from cause to effect, from first principles, and English has used it since 1610. As an adjective it usually sits before its noun: a priori knowledge, a priori grounds. When Jeet Heer, writing in Gravitas in 1996, says New Criterion critics base their authority on "an a priori rejection of the contemporary," the term leans toward judging before examining.

2. 2
   assumedadjective

   Assumed to be true or correct without first being examined or analyzed.

   Investigators cautioned reporters against drawing any a priori conclusion about the cause of the fire.

   The team's a priori assumption that users wanted more features went unexamined until sales collapsed.

   Similarpreconceived, presumptive

3. 3
   adverb

   In a manner grounded in theoretical deduction rather than in empirical observation.

   Some philosophers hold that basic moral principles can be known a priori.

   The physicist argued a priori that the effect must exist, years before any instrument could detect it.

   Similardeductively, theoretically

   Oppositeinductively

   Note

   As an adverb it follows the verb it qualifies: a principle is known a priori, an effect argued a priori. Its opposite is a posteriori, settled by experience rather than by reasoning. Outside philosophy, deductively serves as a rough synonym, with inductively on the other side. Philosophers keep the pairs apart, because a priori concerns where a claim's support comes from, while deductive describes the form of an inference.

4. 4
   obviousadjective

   Evident without needing proof or argument, and obvious by intuition alone.

   That a promise should be kept seemed a priori to him, too obvious to need any defense.

   To a native speaker, the word order feels a priori, obvious in a way that no lesson ever had to explain.

   Similarself-evident, axiomatic, intuitive, obvious

5. 5
   invented languageadjective

   Of a constructed language: created entirely from scratch rather than derived from any existing language.

   She spent six years developing an a priori language for her fantasy novels, coining every root herself.

   The film's alien tongue is fully a priori: none of its vocabulary traces back to any human language.

   Note

   Language inventors use it to sort their own work. An a priori language, such as Klingon from Star Trek or Na'vi, coins its words afresh, while an a posteriori one builds on existing languages. Many projects mix the two, so the label comes in degrees: a language can be more or less a priori. It can also fit a single layer, such as invented words laid over borrowed grammar.

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