The Doorway — Evelyn E. Smith

"It is my theory," Professor Falabella said, helping himself to a cookie, "that no one ever really makes a decision. What really happens is that whenever alternative courses of action are called for, the individuality splits up and continues on two or more divergent planes, very much like the parthenogenesis of a unicellular animal. Since most decisions are hardly as momentous as the individual imagines," Professor Falabella continued, "and since the imagination of the average individual is very limited, many of these different planes--or, as they are colloquially known, space-time continuums -- may exist in close, even tangential relationship."