The Homosexual Matrix the most novel account of the way in which behavioral expression communicates internal states since Charles Darwin's "The Expression of the Emotions in Man and Animals" (1872), but considered his most original contribution to be his explanation of how erotic feeling depends on "resistance", which might consist of any of several impediments to easy access to sexual satisfaction. Begelman called Tripp a skillful writer who was learned on the subject of homosexuality, but whose objectivity was nevertheless open to question. Karlen wrote that Tripp made numerous unjustified claims, such as that homosexual men tend to have a larger than average
The Expression of the Emotions in Man and Animals the actor Henry Siddons in his "Practical Illustrations of Rhetorical Gesture and Action" (1807) and by the anatomist Robert Knox in his "Manual of Artistic Anatomy" (1852) – but abandoned them as unreliable, although the text of "The Expression" is littered with quotations from Shakespeare. Darwin opens the book with three chapters on "the general principles of expression", introducing the rather Lamarckist phrase "serviceable associated habits". With this phrase, Darwin seeks to describe the initially voluntary actions which come together to constitute the complex expressions of emotion. He then invokes a principle of "antithesis", through which opposite states of mind