Emotion in animals specialised form of Occam's razor used in ethology, in which he stated: Charles Darwin initially planned to include a chapter on emotion in "The Descent of Man" but as his ideas progressed they expanded into a book, "The Expression of the Emotions in Man and Animals". Darwin proposed that emotions are adaptive and serve a communicative and motivational function, and he stated three principles that are useful in understanding emotional expression: First, "The Principle of Serviceable Habits" takes a Lamarckian stance by suggesting that emotional expressions that are useful will be passed on to the offspring. Second, "The Principle of
The Expression of the Emotions in Man and Animals induce directly opposing movements. Finally, he discusses a "direct action of the nervous system", in which an overflow of emotion is widely discharged, producing more generally expressed emotions. This is followed by a section (three more chapters) on modes of emotional expression peculiar to particular species, including man. He then moves on to the main argument with his characteristic approach of astonishingly widespread and detailed observations. Chapter 7 discusses "low spirits", including anxiety, grief, dejection and despair; and the contrasting Chapter 8 "high spirits" with joy, love, tender feelings and devotion. Subsequent chapters include considerations of "reflection and meditation" (associated