The Expression of the Emotions in Man and Animals usually been viewed in its relationship to Darwin's conception of "natural selection" as the central mechanism of evolutionary development, which he probably grasped some time around September 1838. These notes have a tentative and fragmented quality, especially in Darwin's descriptions of conversation with his father (a successful doctor with a special interest in psychiatric problems) about recurring patterns of behaviour in successive generations of his patients' families. Darwin was anxious about the materialistic drift in his thinking – and of the disrepute which this could attract in early Victorian England – at the time, he was mentally preparing for marriage
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