It is interesting that the term mystic is used in this derogatory sense to mean anything we cannot segmentize and count. The odd belief prevails in our culture that a thing or experience is not real if we cannot make it mathematical, and that somehow it must be real if we can reduce it to numbers. But this means making an abstraction out of it … Modern Western man thus finds himself in the strange situation, after reducing something to an abstraction, of having then to persuade himself it is real. … the only experience we let ourselves believe in as real, is that which precisely is not.

Existence (1956) p. 39; also published in The Discovery of Being : Writings in Existential Psychology (1983), Part III : Contributions to Therapy, Ch. 6 : To Be and Not to Be, p. 94 - Existence (1958)