A.J. Festugière (1898-1982), Epicurus and His Gods
, tr. C.W. Chilton (Cambridge: Harvard University Press, 1956), p. 14:
What strikes me as essential is the fact that adhesion to Hellenistic religious sects was the result of a free choice by the individual. Nothing compelled him to betake himself to this or that new deity, Isis, the Syrian Aphrodite, the Phrygian Great Mother, etc.: there was no compulsion because these gods were not bound to any city. He was not drawn by custom to worship them. If he went to them, it was from the impulse of a personal religious conviction, to give satisfaction to a need of his soul. That, in religion, is a new and very remarkable thing.