Pneuma (πνεῦμα‎‎, Lat. spiritus) is connected etymologically with πνέω‎‎, breathe or blow, and has a basic meaning of ‘air in motion’, or ‘breath’ as something necessary to life. In Greek tragedy it is used of the ‘breath of life’ and it is the ‘Spirit’ of the New Testament. In early Greek thought pneuma is often connected with the soul; in Aristotle it frequently denotes ‘warm air’, sometimes ‘heat’, and the term is also used of seismic winds which are trapped within the earth. Its precise meaning, then, must always be determined in its context. The word may have been used first by Anaximenes (1) of Miletus to describe both elemental air in motion in the world, and ‘psychic air’ in man. ‘Psychic pneuma’ also constitutes the soul and underlies sensory and motor activities in a number of ancient medical theories. In Hippocratic and post-Hippocratic writings (see hippocrates(2)) it is widely used of inspired air or breath inside the body, with no apparent reference to any particular theory. In the medical theory of Erasistratus, ‘vital pneuma’ travels from the lungs via the heart into the arteries. One ancient medical sect, the ‘Pneumatic’ (see pneumatists), was called after its central use of such concepts. Pneuma-theory forms a cornerstone of Stoic physics (see stoicism), and the Stoics are particularly associated with the doctrine that pneuma provides the universe both with cohesion and its dynamic properties.