Syllogistic logic online
- This site contains an online program for studying Aristotle's syllogistic logic. The theory of Aristotle's ancient logic is also presented.
- http://aristotelianlogic.glashoff.net

On Dialectic
- By St. Augustine. Latin original together with translation by J. Marchand.
- http://www.georgetown.edu/faculty/jod/texts/dialecticatrans.html

Peter of Spain (Petrus Hispanus)
- Life and work of 13th century logician and author of the Tractatus; from the Stanford Encyclopedia by Joke Spruyt.
- http://plato.stanford.edu/entries/peter-spain/

Aristotle's Logic
- Introductory article by Garth Kemerling.
- http://www.philosophypages.com/hy/2n.htm

Logic
- Entry in the Catholic Encyclopaedia (1917), dominated by a historical survey from Indian and Pre-Aristotelian philosophy to the Logic of John Stuart Mill.
- http://www.newadvent.org/cathen/09324a.htm

Square of Opposition
- Article in the Stanford Encyclopaedia of Philosophy, by Terence Parsons.
- http://plato.stanford.edu/entries/square/

Aristotle's Reform of Paideia
- Article by Evelyn Barker, arguing that the principal aim of Aristotle's Organon was to reform the contemporary paedagogical role of dialectic.
- http://www.bu.edu/wcp/Papers/Anci/AnciBark.htm

Scholasticism
- Online text by Joseph Rickaby (1908).
- http://www.nd.edu/Departments/Maritain/etext/scholas1.htm

Scholastic Logic
- Chapter Two of Joseph Perrier's "The Revival of Scholastic Philosophy in the Nineteenth Century" (1909).
- http://www.nd.edu/Departments/Maritain/etext/perrier2.html

Medieval Theories of Modality
- Article at the Stanford Encyclopaedia of Philosophy.
- http://plato.stanford.edu/entries/modality-medieval/

Medieval Theories of Analogy
- Entry in the Stanford Encyclopaedia of Philosophy, by E. Jennifer Ashworth.
- http://plato.stanford.edu/entries/analogy-medieval/

The Summulae of John Buridan
- A critical introduction by Gyula Klima.
- http://www.fordham.edu/gsas/phil/klima/Intro.htm

Mediaeval Logic and Philosophy
- Resource maintained by Paul Vincent Spade at Indiana University.
- http://pvspade.com/Logic/