Karl Popper says that a scientific statement is one that is falsifiable -- there are clear, observable tests you might apply to that statement which would prove it wrong. If clean, solid billiard balls in motion sometimes collided and then simply stuck together and lay still, instead of bouncing apart, then Newton's Laws of Motion would have to be reconsidered. Statements like "Rapture is coming" are less scientific than Newton's Laws, by these lights, because no one can ever positively prove that rapture is not, at some point, coming. You can't make any observations of the future. "Rapture is coming on January 1, 2000 of the western calendar" is a more scientific statement (and also a provably false one -- everyone observed that Rapture failed to arrive on that day).

Is "Rapture is coming" true or false? The event about which it potentially speaks is unavailable in the world of the present and its known history -- it lies ahead of us in time. It's not part of what can be observed. So perhaps statements like this one have to be simply set aside, when we are interested in truth. Statements about the future can only be retrospectively true.

Billiard balls have never been seen to collide and then stick together -- yet. Rapture has not come -- yet. So aren't they both statements about an uncertain future? The difference is that one of them succeeds in being true about much of the known past and present. The other has never applied to anything, and so there is no evidence for or against. Balls flying apart is evidence for Newton's Laws; each and any time a fast-moving billiard ball sticks to another ball and they both stop moving, evidence against has appeared. Any strong truth claims, according to Popper, come with this kind of clear specification of what, exactly, would be a disaster for the claim.

But sometimes I think about the problem of verification the other way -- from the perspective of the person who makes a truth claim that they really believe. When you say that you believe something is true, fully true, you are inviting any and all potential observers to agree. You are challenging all the inhabitants of the entire future to check your work -- throwing down the gauntlet of what is known, now, before the specter of all that will ever be known, by every new face and facet of the entire future history of observing beings. It's a brash thing to do.

People know, most of the time, that their perspective is provisional. When pressed, most people will tend to hedge, and say "I wouldn't bet my life on it, but I think that X," or "It seems to me that X." Even the expression "I believe," as we use it in English, has a kind of qualification buried in it. Martyrs and loners, prophets, in that brave act of extending their gnosis as far as it will go, say "This thing is what I believe, and I will stand by it." The very effort that a believer expends, the amount of nobility it takes to wholeheartedly believe something, is a testament to the unlikeliness and provisional character of being right about anything.

There's a scene in the novel "Contact" where a scientist is asked to place her nose just at the top point of the swing arc of a massive pendulum. The pendulum is released, allowed to swing away, then back toward her. Knowing Newton's Laws, she knows that the pendulum cannot -- it cannot -- swing back up and hit her, no matter how much momentum it seems to have. But the dramatic question of the scene is, "Does she truly believe it? Will she be struck anyway?" She does feel afraid, but she does manage to hold still.

I think -- I believe -- that babies are made by sperm and egg uniting, with the sperm actually entering the egg, and the whole mass turning into a human child over the course of nine months. I strongly believe that this is true; it does not live in the realm of "theory" for me, in the way that plate tectonics is a theory, which might come in for modification at some point. I don't think the idea of sperm uniting with egg (historically new though it may be) will ever be subject to any modification. Elaboration, surely, but not fundamental alteration.

But if you put a gun to my head, and asked me again where babies come from, I might admit that I have not actually seen the fertilization process firsthand. I have seen it on television and in films, have read about it in books from different sources, and have seen its effects in many situations. I know people who have observed sperm firsthand under a piece of ground glass.

But there is colder wind, a skeptical touch, which makes the whole edifice sway just a little, like a tower seen through a heat haze.

I'm an idealist -- I want to know that the tower will stand forever.