I often find myself in a position where I realize that taking my own life would be very easy. Suppose I am about to cross the street, or am rock climbing; how simple and quick it would be to take one step, just one step, in front of a car or off a cliff. In all likelihood I wouldn't even feel any pain. In this way there seem many scenarios wherein the effective "barrier" to suicide seems practically nonexistent. I must stress: my contemplation of suicide in such instances has nothing to do with depression or even emotion, nor do I mean to make light of those who suffer from such grief; rather, I find the extreme ease with which I may conceptually commit catastrophic acts somewhat counter-intuitive. After all, what is there, really, to dissuade me? Suppose that I am an atheist. what rationale exists that might prevent me from killing myself? For one who is certain (1) that there exists no afterlife, and, further, (2) that there is no consciousness after death (i.e., I won't "miss" anything of life or...

Given your assumptions that there is no afterlife or consciousness after death, I can think of two kinds of reasons not to commit suicide (though these needn't decide against suicide in all cases): (1) Moral reasons: Killing yourself may result in harm to others (e.g., to one's dependents, or to the truck driver who is traumatized by killing you), and we sometimes have obligations not to impose such costs on others. The fact that you won't be around after your death doesn't mean that it wouldn't be wrong for you to impose such costs. (Similar issues arise with respect to environmental problems that we create that will affect future generations.) (2) Self-interested reasons: Even though you won't be around after your suicide, there may be a sense in which your life would be better for you if you decide not to kill yourself. If we compare the two lives (the one you live by killing yourself now versus the one you would have lived had you not killed yourself now), it could turn out that not killing yourself...