1. Ancient
   1. Pre-Socratic
      1. Milesian
         1. Thales
         2. Anaximander
         3. Anaximenes
      2. Pythagoreans
         1. Pythagoras
         2. Philolaus
         3. Alcmaeon
         4. Archytas
      3. Heraclitus
      4. Eleatic School
         1. Xenophanes
         2. Parmenides
         3. Zeno of Elea
         4. Melissus of Samos
      5. Pluralists
         1. Empedocles
         2. Anaxagoras
      6. Atomists
         1. Leucippus
         2. Democrates
         3. Metrodorus
      7. Pherecydes
      8. Sophists
         1. Gorgias
         2. Protagoras
         3. Antiphon
         4. Prodicus
         5. Hippias
         6. Thrasymachus
         7. Callicles
         8. Critias
         9. Lycophron
      9. Diogenes
   2. Hellenistic
      1. Metrodorus the Younger
      2. Arcesilaus
      3. Archimedes
      4. Clitomachus
      5. Peripateticism
         1. Theophrastus
         2. Strato
         3. Alexander of Aphrodisias
      6. Cyrenaicism
         1. Aristippus of Cyrene
      7. Epicureanism
         1. Epicurus
         2. Metrodorus of Stratonicea
         3. Zeno of Sidon
         4. Philodemus
         5. Lucretius
      8. Stoicism
         1. Zeno of Citium
         2. Chrysippus
         3. Posidonius
         4. Cleanthes
         5. Epictetus
      9. Neo-Pythagoreanism
         1. Apollonius of Tyana
         2. Numenius of Apamea
      10. Neo-Platonism
          1. Plotinus
          2. Porphyry
          3. Iamblichus of Chalcis
      11. Pyrrhonism
          1. Pyrrho
          2. Aenesidemus
          3. Timon
      12. Cynicism
          1. Antisthenes
          2. Diogenes of Sinope
          3. Menippus
          4. Crates of Thebes
          5. Demetrius
      13. Philo of Larissa
      14. Philo of Alexandria
      15. Agrippa
      16. Platonism
          1. Speusippus
          2. Carneades
          3. Antiochus of Ascalon
          4. Xenocrates
          5. Plutarch
   3. Classical Greek
      1. Socrates
      2. Euclid of Megara
      3. Plato
      4. Aristotle
      5. Stilpo
2. Medieval
   1. Augustine
   2. Boethius
   3. John Scottus Eriugena
   4. Maimonides
   5. Roger Bacon
   6. Anselm of Canterbury
   7. Peter Abelard
   8. Thomas Aquinas
   9. John Duns Scotus
   10. William of Ockham
3. Renaissance
   1. Mirandola
   2. Erasmus
   3. Machiavelli
   4. Thomas More
   5. Paracelsus
   6. Copernicus
   7. Montaigne
4. Early Modern
   1. Francis Bacon
   2. Rene Descartes
   3. Hobbes
   4. Henry More
   5. Arnauld
   6. Malebranche
   7. Benedict Spinoza
   8. Lady Anne Conway
   9. John Locke
   10. Gottfried Leibniz
   11. Berkekey
   12. Wolff
   13. Rousseau
   14. Immanual Kant
   15. Bentham
   16. Schiller
   17. Malthus
   18. Fichte
5. 19th Century
6. Contemporary