If you went back to, I would guess, 1946, and worked to prevent your parents’ marriage in 1947, you would still have existed in that year; you would not go out of existence just because you had influenced events. The same would apply even if you had only been in 1946 one microsecond before shooting the man who would otherwise have become your father.

Time is said to be the fourth dimension, but it differs from the other three in one conspicuous way—our consciousness moves along it. From past to present only, alas. Time itselfdoes not flow, no more than, say, width can flow. Our minds flicker from one instant of time to the next. This analogy was my starting point. I reasoned that if consciousness can move in one direction, it can move in the other direction as well. It took me fifty years to work out the details, however, and make what I call a flashback possible.