Either God is a Mystery or He is nothing at all. - Walter Terence Stace

It is certainly the case that there can exist an atheistic mysticism, a mystical experience naked and not clothed in any religious garb.

The most important, the central characteristic in which all fully developed mystical experiences agree, and which in the last analysis is definitive of them and serves to mark them off from all other kinds of experiences, is that they involve the apprehension of an ultimate nonsensuous unity in all things, a oneness or a One to which neither the sense nor the reason can penetrate.

It is a commonplace that eternity is not an endless prolongation of time, has nothing to do with time. Eternity is a characteristic of the mystical experience. The word eternity doubtless meant originally endlessness of time, which must count, therefore, as its literal meaning. But in its religious and metaphysical use it is a metaphor for the characteristic of the experience. For in that experience time drops away and is no more seen.