 That ordinary acts might have such an existence-inducing nature – that the people they bring into flawed existences would not, indeed, could not have ever existed at all in the absence of those acts – is related to the phenomenon Gregory Kavka described as the “precariousness” of existence (Kavka 1982, 93). We understand that the identity of each person who ever comes into existence – the coming into existence, that is, of any one particular person in place of any nonidentical distinct person – depends, among other things, on just who the genetic parents of that person happen to be. As Parfit observes, the woman who wonders who she would have been had her “parents married other people” “ignores the answer,” which is “no one” (Parfit 1987, 351). But it is not just whom one procreates with that determines the identity of one’s offspring. It is also what Parfit described as the “timing and manner” of conception. When the act of conceiving a child is moved forward or backward in time by months or even moments, or when the manner of conception is itself altered (accomplished, e.g., via in vitro fertilization rather than coitus), the result, very probably, will be the conception of a distinct child altogether. After all, any difference in timing or manner of conception very probably will place a distinct inseminating sperm cell (out of hundreds of millions!) in proximity to the ovum or even result in a distinct ovum being inseminated. And a distinction in sperm and egg cells would seem in most cases sufficient to insure the conception of a distinct child (Parfit 1987, 351–55; 2011 vol. 2, 217–231). Moreover, the exact timing and manner of conception is itself highly susceptible to variations in whatever complex chain of acts and events it is that has come before. Much of what has been done in human history, had it been done differently, would surely have undone the conceptions of vast numbers of people. “[H]ow many of us could truly claim, ‘Even if railways and motor cars had never been invented, I would still have been born’?” (Parfit 1987, 361).