“[speaking of going back in time] I’d particularly like to go back to my own childhood, see if things look as I recall them.”
Ira blinked. “Run a chance of running into yourself?”
“Well . . there are paradoxes, are there not?”
“How? If I’m going to, then I did. That old cliche about shooting your grandfather before he sires your father, then going fuff! like a soap bubble—and all descendants, too, meaning both of you among others—is nonsense. The fact that I’m here and you’re here means that I didn’t do it—or won’t do it; the tenses of grammar aren’t built for time travel—but it does not mean that I never went back and poked around. I haven’t any yen to look at myself when I was a snot-nose; it’s the era that interests me. If I ran across myself as a young kid, he—I—wouldn’t recognize me; I would be a stranger to that brat. He wouldn’t give me a passing glance; I know, I was he.”" -Heinlein, Time Enough for Love, p. 358.