Stanford University
Stanford Encyclopedia of Philosophy: Modal Logic
Explains modal logic by means of logical notation. Somewhat difficult for a non-specialist to appreciate. However, the introductory section does provide a general definition of "modal logic."
Internet Encyclopedia of Philosophy
Internet Encyclopedia of Philosophy: Immanuel Kant (1724 1804)
A very in-depth look at the philosophical ideas of Immanuel Kant on subjects such as ethics, rationalism, and much more.
University of Sydney (Australia)
The Write Site: What Are Sentence Fragments?
This learning module provides a clear explanation of sentence fragments. Hints for finding sentence fragments are provided, along with explanations about how to fix them.
Stanford University
Relevance Logic/stanford Encyclopedia of Philosophy
Discusses the topic of relevance (or relevant) logics. Presents the theory and applications of relevance logic, which attempts to resolve "fallacies of relevance."