The _third_ period of Stoicism is Roman.

In this period, we have Cato the Younger, who invited to his house the philosopher Athenodorus; and, under the Empire, the three Stoic philosophers, whose writings have come down to us--SENECA (6 B.C.-65 A.D.), EPICTETUS (60-140 A.D.), who began life as a slave, and the Emperor MARCUS AURELIUS ANTONINUS (121-180 A.D.).

Stoicism prevailed widely in the Roman world, although not to the exclusion of Epicurean views.
The leading Stoical doctrines are given in certain phrases or expressions, as 'Life according to Nature' (although this phrase belongs also to the Epicureans), the ideal 'Wise Man,' 'Apathy,' or equanimity of mind (also an Epicurean ideal), the power of the 'Will,' the worship of 'Duty,' the constant 'Advance' in virtue, &c.

But perspicuity will be best gained by considering the _Moral_ system under four heads--the Theology; the Psychology or theory of mind; the theory of the Good or human happiness; and the scheme of Virtue or Duty.
I .-- The THEOLOGICAL doctrines of the Stoics comprehended their system of the Universe, and of man's position in it.

They held that the Universe is governed by one good and wise God, together with inferior or subordinate deities.