Philosophy: Biographies
- Adam Ferguson
- Adelard of Bath
- al-Ghazali
- Alain de Lille
- Alexander Bain
- Alexander of Aphrodisias
- Alexander of Hales
- Alexander of Tralles
- Alfred Tarski
- Anaxagoras
- Anaximander
- Anaximenes
- Anthony Ashley Cooper 3d earl of Shaftesbury
- Antisthenes
- Aristippus
- Aristotle
- Arthur Oncken Lovejoy
- Arthur Schopenhauer
- Auguste Comte
- Averroes