Definition

1. Adjective:

   • Based on hypothesis, theory, or deduction rather than on experience or observation: Describes reasoning, knowledge, or arguments that proceed from a general principle or assumed cause to its necessary effects.
   • Presumed or assumed to be true without analysis: Describes a judgment made prior to or independently of investigation of the specific case.

2. Adverb:

   • In a way based on theoretical deduction rather than empirical observation: Describes the manner of deriving a conclusion logically from a premise, without reference to specific facts.

Usage Examples

• Adjective:

  • His argument was purely a priori, relying on logic rather than data.
  • We can make an a priori assumption about human nature for this model.

• Adverb:

  • One can reason a priori that all bachelors are unmarried.
  • She concluded a priori that the plan would fail, without examining the details.

Advanced Usage

• Philosophical Context: In philosophy, especially in the work of Immanuel Kant, a priori knowledge is knowledge that is independent of experience (e.g., "All triangles have three sides"). It is often contrasted with a posteriori knowledge, which depends on experience.

  • Kant argued that the propositions of mathematics are synthetic a priori judgments.

• Legal Context: Used to describe reasoning or decisions based on a fixed rule or principle applied to a case, rather than on the case's specific circumstances.

  • The judge rejected an a priori application of the rule, insisting on examining the evidence.

Variants and Related Words

• A priority (n., rare): The quality or condition of being a priori.
• Apriorism (n.): The philosophical doctrine that knowledge can be derived independently of experience.
• Aprioristic (adj.): Relating to or characterized by a priori reasoning.

Synonyms

• Deductive: Reasoning from the general to the particular.
• Theoretical: Concerned with or involving theory and hypothesis rather than practical application.
• Presupposed: Assumed beforehand.

Antonyms

• A posteriori: Based on observation, experience, or empirical evidence.
• Empirical: Based on, concerned with, or verifiable by observation or experience.
• Inductive: Reasoning from specific observations to broader generalizations.

Related Phrases and Idioms

• A priori reasoning / argument / knowledge: Standard collocations using the term.
  • His conclusion was the result of a priori reasoning.
• Assume a priori: To presuppose something without proof.
  • We cannot assume a priori that the system is flawless.

Adjective

1. based on hypothesis or theory rather than experiment
2. involving deductive reasoning from a general principle to a necessary effect; not supported by fact
   • an a priori judgment

Adverb

1. derived by logic, without observed facts