"That which is known as the Christian religion existed among the ancients, and never did not exist; from the beginning of the human race until the time when Christ came in the flesh, at which time the true religion, which already existed began to be called Christianity." Saint Augustine of Hippo, Retractions, Book One, Part 12, "One Book on the True Religion."
I found this quote to be very interesting (edit: the quote is not rarely stated on the net). I haven't sourced it, so it may be a false. But if it is real, then it is true that there is an esoteric (secret) aspect of Christianity, which may even be traceable back to Egypt, as Gurdjieff sugested.
Saint Aquinas may have said it metaphorically, to fool the clergy (or something?). But I highly doubt it. There are powerful parallels which would be almost impossible to occur randomly. (and since we all know that Tao is not random...)