Psychologists note that we tend to make sharp divisions among items arranged in a spectrum. Suppose, for instance, that we have an array of drinking vessels, with what is clearly a mug on the left and what is clearly a glass on the right. From left to right, the intervening vessels become less mug-like and more glass-like. Am I making sense? Okay, at some point, I am going to say, "The ones from here on," gesturing to the right, "are glasses." At some point, you are going to say the same. The catch is that we will probably not make the choice at the same point. However, the choices we make are firm. They call it "discrete perceptual discontinuities." What a grand phrase that is.
We could, at that time, spend a few hours defending our choices and ridiculing the choices of others, and nothing would be lost but time. Except. The same tendency exhibits itself in any situation where a spectrum of possibilities exists. When are we viable entities? In the womb? At the moment of birth? When do we die? How much radiation risk is too much?
We are not happy with fuzzy answers to many of life's questions, so we set firm boundaries. And that's the problem. We assume all along that those boundaries are natural ones. They aren't. We don't discover boundaries; we create them. There is no magical moment when a person becomes alive or when a person becomes not alive. There's a fuzzy area between and someone, sometime, has to decide just where the boundary is. Sort of like in a football game when the referee runs up to a pile of players and plants his foot. That place is where the ball belongs. Not that the ball is really there, but because the ref has made the decision.
Or, to pursue the sports analogy further, remember the old story of the three umpires talking? The first says, "Some is strikes and some is balls, and I calls them the way they is." The second one says, "Some is strikes and some is balls, and I calls them the way I sees them." The third (it's always the third) says, "Some is strikes and some is balls, but they aint nothing till I calls them." Now, this is not a vindication of Schroedinger's cat, nor evidence of how reality flexes, but simply an illustration of how we make decisions about how events should be punctuated.
The problem is, obviously, that we kill each other over where events should be punctuated. Doesn't seem right, does it? A sane world would discuss costs and benefits for decisions such as "Should we have nuclear power?" or "When should we allow an abortion?" or "When can we terminate the life of a person?" If we keep in mind the rights of a human (which are not, T. Jefferson to the contrary, inalienable), the needs of society, and the future of the planet, we might come to some sort of rational policy set. Of course, the minute we try it, someone will say that god has told him to blow us up for blasphemy. Sigh.