Abelard Peter; Absolute; absorption; abstraction; absurd; Abunaser; accent fallacy of; accident; accident fallacy of; action theory; act - rule utilitarianism; actuality - potentiality; Addams Jane; addition; ad hominem argument; adiaphora; Adler Alfred; Adorno Theodor Wiesengrund; aesthetic; affirmative conclusion from negative premise; affirmative proposition; affirming the alternative; affirming the consequent; a fortiori; agent; agnosticism; agreement method of; aisthaesis; aition; akrasia; Albert the Great; aletheia; Alexander Samuel; Algazel; alienation; Alpharabius; alternation; alternative occurrence; Althusser Louis; altruism; ambiguity; amoral; amphiboly; analogy; analysis; analytic philosophy; analytic - synthetic; anamnaesis; anankae; Anaxagoras of Clazomenae; Anaximander; Anaximenes; andreia; Angst; anima; animal rights; animals; animism; Anscombe G.E.M.; Anselm - Anselm of Canterbury; antecedent; Anthony Susan Brownell; anthropic principle; anthropomorphism; Antisthenes; antithesis; anxiety; apeiron; apodeictic; aporia; appearance - reality; apperception; Appiah Kwame Anthony; applied ethics; a priori; A proposition; Aquinas Thomas; archae; Archimedes; Arendt Hannah; Ares; aretae; argument form; argumentum; Aristippus; aristotelianism; aristotelian logic; Aristotle; Armstrong David M.; Arnauld Antoine; Arrow Kenneth Joseph; artificial intelligence; assent; assertoric; association; association of ideas; assumption; ataraxia; attribute; Aufklaerung; Augustine; Austin John; Austin John Langshaw; authenticity; authority appeal to; autonomy - heteronomy of the will; Averroes; Avicebron; Avicenna; axiology; Ayer Alfred Jules;