According to its doctrines the normal as well as diseased actions of the body were to be referred to the operation of the pneuma or universal soul.
It was on this field that he most vehemently attacked the prevailing atomistic and materialistic views of the methodic school, and his conception of the pneuma became in some respects half metaphysical.
Incidentally we meet there with the doctrines of Pneuma and of tension, of the corporeal nature of the virtues and the affections, and much more to the same effect.
From the elements the one substance is transformed into the multitude of individual things in the orderly universe, which again is itself a living thing or being, and the Pneuma pervading it, and conditioning life and growth everywhere, is its soul.
In the rational creatures - man and the gods - Pneuma is manifested in a high degree of purity and intensity as an emanation from the world-soul, itself an emanation from the primary substance of purest ether - a spark of the celestial fire, or, more accurately, fiery breath, which is a mean between fire and air, characterized by vital warmth more than by dryness.
In this primitive Pneuma there must reside the utmost tension and heat; for it is a fact of observation that most bodies expand when heated, whence we infer that there is a pressure in heat, an expansive and dispersive tendency.