ThymosThe word "thymos" was used in ancient Greece to denote the driving emotions of the human soul.
The heroes of Homer's poems are driven by thymos and thymos dies when the hero dies. It is not "menos" (the vital force) but an unconscious psychic force. Thymos encompasses not only the mind but also the heart and the lung: all the things that keep one alive and functioning. Homer's thymos is similar to Freud's unconscious in that it drives sexual desire and primal instincts. Thymos is responsible for the "character" of people.
Empedocles calls thymos the "seat of life."
Platon writes that the psyche/soul is made of three substances: logos/nous (reasoning), eros (love) and thymos (passion).
See the Oxford dictionary of philosophy (and avoid at all costs the Wikipedia article!)
See Piero Scaruffi's website for thymos-related articles.