Structure
Expression opens with three chapters (1–3) entitled "General Principles of Expression", where Darwin introduces three principles:
- "The principle of serviceable associated Habits" – describes how initially voluntary actions constitute complex expressions of emotion by association of habit.
- "The principle of Antithesis" – explains how opposite mental states induce directly opposing movements.
- "The principle of actions due to the constitution of the Nervous System, independently from the first of the Will, and independently to a certain extent of Habit" – discusses the interplay between physiological reactions (e.g., sweating, muscle trembling, blushing) and emotional experiences.
In the following chapters (4–6), Darwin presents his findings on modes of emotional expression peculiar to particular species, including humans.
Chapters 7–8 contain Darwin's observations on "low spirits" (anxiety, grief, dejection, and despair) and "high spirits" (joy, love, tender feelings, and devotion). Darwin claims that high spirits, exemplified by joy, find their purest expression in laughter.
Subsequent chapters (9–13) discuss various emotions and their expression. In his discussion of the emotion "disgust", Darwin notes its close links to the sense of smell and conjectures an association with offensive odours. In chapter 13 (which highlights the emotional states of self-attention, shame, shyness, modesty, and blushing), Darwin describes blushing as "the most peculiar and the most human of all expressions".
Darwin closes the book with chapter 14, where he summarises his central argument, demonstrating how human emotions link mental states with bodily movement. He argues that these expressions are genetically determined and derive from purposeful actions observed in animals. He comments on the book's implications, proposing a single origin for the entire human species, with universal human expressions. Darwin emphasises the social value of expression, especially the emotional communication between mother and child.