Other physical theories were borrowed from Heraclitus, and Marcus constantly alludes to these, such as the " downward and upward " round of the elements as they emanate from the primary Fire, air passing into fire, fire into earth, earth into water and so back again, and the famous doctrine that all things are in flux.
Man consists of Body, Soul, Intelligence, or Flesh, Pneuma, and the Ruling Reason. But the ψυχή (soul) can be looked upon in two ways, as πνευμάτιον, an exhalation from blood, and as ἡ νοερά, ἡ λογικὴ ψυχή, i.e. the ruling Reason. It is the latter, a "morsel" or "efflux" from the Divine, which constitutes the real man. Marcus often speaks of this rational nature  of a man as his daemon, or genius enthroned within him, and makes the whole problem of life depend upon how this Reason treats itself. As all that is rational is akin, we are formed for fellowship with others and, the universe being one, what affects a part of it affects the whole. Reason is as a Law to all rational creatures, and so we are all citizens of a World-state. In this cosmopolitanism the Stoics approached the Christian view, ethics being divorced from national politics and made of universal application. It was no cloistered virtue the Stoics preached, showing how a man can save his own soul, but a practical positive goodness; though it cannot be denied that the claims of αὐτάρκεια
- ἄνω κάτω. vi. 17; ix. 28.
- iv. 46.
- ἅπαντα ῥεῖ, ii. 17; iv. 3 ad fin., 36; v. 10; vi. 15; vii. 25; ix. 19; x. 7.
- iii. 16; xii. 3.
- v. 33; vi. 15, or ζωή, an inhalation from the air.
- ii. 1; ii. 4; v. 27.
- xi. 1.
- ii. 17; iii. 7, 16; v. 27, etc., and he calls this God, iii. 5; v. 10; xii. 26.
- iv. 4.
- vi. 30.