Definition

1. Adjective:

   • Derived from or requiring evidence, observation, or experience: Describes knowledge, reasoning, or arguments that are based on actual evidence or empirical data rather than theory or pure logic.
   • Involving inductive reasoning: Pertaining to reasoning that moves from specific observed facts or effects to general principles or causes.

2. Adverb:

   • In a way that is based on or derived from observation or experience: Describes the manner of knowing or proving something through empirical evidence.

Usage and Examples

• Adjective:

  • Scientific theories are often a posteriori constructs, built upon accumulated experimental data.
  • The detective's a posteriori reasoning led him from the clues at the crime scene to the identity of the culprit.

• Adverb:

  • We can only know the outcome of the experiment a posteriori, after we have conducted it and seen the results.
  • The philosopher argued that certain truths about the world can be known solely a posteriori.

Advanced Usage and Nuances

• In philosophy (especially epistemology): The term is often contrasted with "a priori" (knowledge independent of experience). "A posteriori" knowledge depends on sensory experience.
  • The statement "Water boils at 100°C at sea level" is an a posteriori truth because it requires empirical verification.
• In logic and statistics: Refers to conclusions drawn after analyzing data.
  • An a posteriori probability is updated based on new evidence, unlike a prior assumption.

Variants and Related Words

• A posteriori probability (noun phrase): In statistics, the probability of an event updated after taking into consideration new evidence. (e.g., )
• Empirical (adj): Based on observation or experience rather than theory. (A close synonym in many contexts.)
• Inductive (adj): Characterized by the inference of general laws from particular instances. (Related to the reasoning process.)

Synonyms

• Empirical
• Experiential
• Inductive
• Ex post facto (particularly in legal contexts, meaning "after the fact")

Antonyms

• A priori: Based on theoretical deduction rather than empirical observation.
• Deductive: Reasoning from general principles to specific instances.
• Theoretical

Related Phrases and Usage Notes

• "A posteriori justification": Validation or reasoning provided after an event or discovery.
  • His hypothesis was supported by a posteriori justification from the unexpected results.
• The term is most commonly used in academic, scientific, and philosophical contexts. It is typically not used in everyday casual conversation.

Adjective

1. requiring evidence for validation or support
2. involving reasoning from facts or particulars to general principles or from effects to causes
   • a posteriori demonstration

Adverb

1. derived from observed facts