… theos, the Greek word which we have in mind when we speak of Plato’s god, has primarily a predictive force. That is to say, the Greeks did not, as Christians or Jews do, first assert the existence of God and then proceed to enumerate his attributes, saying “God is good,” “God is love” and so forth. Rather they were so impressed or awed by the things in life or nature remarkable either for joy or fear that they said “this is a god” or “that is a god.” The Christian says “God is love,” the Greek “Love is theos,” or “a god.” As another writer [Georges M. A. Grube] has explained it: “By saying that love, or victory, is god, or, to be more accurate, a god, was meant first and foremost that it is more than human, not subject to death, everlasting. … Any power, any force we see at work in the world, which is not born with us and will continue after we are gone could thus be called a god, and most of them were.”
In this state of mind, and with this sensitiveness to the superhuman character of many things which happen to us, and which give us, it may be, sudden stabs of joy or pain which we do not understand, a Greek poet could write lines like: “Recognition between friends is theos.” It is a state of mind which obviously has no small bearing on the much-discussed question of monotheism or polytheism in Plato, if indeed it does not rob the question of meaning altogether.
W. K. C. Guthrie, The Greek Philosophers: From Thales to Aristotle, pp. 10-11