Face of a frightened soldier (left); the human face in an animal state of fear (right). Etching by B. Picart, 1713, after C. Le Brun.

Le Brun's depiction of the passions is supported by his theory of the passions, which is delineated in the 'Conférence'. In Cartesian style, each compound passion is an organisation of the six simple passions of admiration, love, hatred, desire, joy and sadness. For instance, jealousy is a composite of love and hate; despair "is a strong persuasion of not being able to obtain what we desire"