 "Pneuma" is necessary for life, and as in medical theory is involved with the "vital heat," but the Aristotelian "pneuma" is less precisely and thoroughly defined than that of the Stoics.In Stoic philosophy, "pneuma" is the concept of the "breath of life," a mixture of the elements air (in motion) and fire (as warmth).For the Stoics, "pneuma" is the active, generative principle that organizes both the individual and the cosmos.