Based on a series of lectures given by Leonard Peikoff in 1981, Principles of Grammar offers not only an organized survey of grammatical rules and principles but their connection to the principles of clear thinking and clear writing. "At the end of the course," says Dr. Peikoff, "you should be able to see every grammatical rule, directly or indirectly, as a consequence or expression of some essential requirement of the human mind," not "a simply a...