"X exists"-space


The logical space of all propositions of the form "X exists" is tentatively explored..

Consider these propositions: "a bird exists."; "a Swinhoe's storm-petrel exists"; "the Roc from the Sinbad tales exists". The first two are true in our world, and the last is not, although it may have been true long ago (extremely large fossil birds, not to mention dinosaur fossils, are found everywhere.) We can assert the truth or falsity of these 3 propositions with great confidence, due to our breadth of knowledge of the world. If you don't know of or have never seen a Swinhoe's storm-petrel, a quick internet search will convince you that they're the real deal; while we know the Roc does not exist - if it did, it would certainly be known to us by virtue of its voracious appetite and lack of natural predators. In other words, there is lots of evidence for the first two, while the complete lack of evidence for the last is more than enough reason for us to disbelieve in the Roc.

Now consider some more propositions: "an asteroid whose surface has been etched by collisions with space debris into a perfect copy of the entire works of Robert Hooke (both published and unpublished) exists"; "a green ostrich-like bird with ten necks, each capped not with a head but with a different brand of MP3 player, exists"; "an all-powerful being who created the entire universe exists". None of these are true; but I'm getting ahead of myself here. Let me say first that no one thinks that the first two are true, while many people think that the last one is true. If we were to pile up the evidence for any of these three propositions, however, we would see that there is none that stands up to scrutiny.

Of course, these things might exist - after all, they don't contradict logic - so how should we decide? Maybe we need to get some idea of the a priori likelihood of anything existing. It is my contention that this likelihood is extremely low. Consider this picture:



This represents what I call "X exists"-space. The top hemisphere contains propositions of the form "X exists"; the bottom is the opposite of the top, containing the negated expression "X does not exist". By usual convention, red represents FALSE and green represents TRUE. The tiny green islands in the upper red sea represent our knowledge; the things that we can assert with confidence. They have irregular shapes, as our knowledge grows in unpredictable ways. But they remain tiny. You can try it yourself: come up with some crazy entities like I did, and see if you have any reason to assert that it exists. Here's a hint: for every entity that does exist, we can construct many more that do not (the mp3 player trick works pretty well).

At this point in the story, instead of agreeing with me about the last proposition (about the creator of the universe), the world's population splits along some interesting lines; roughly, into theists, deists, agnostics, and atheists. To retain intellectual integrity, a theist must claim to possess some kind of evidence that a deity exists, which these days is usually either the design argument, or the argument from personal experience. I will not deal with these here; they were refuted long ago. A deist doesn't need to have evidence, but is also in danger of losing integrity unless they can come up with some sort of a priori argument why that last statement ("an all-powerful being who created the entire universe exists") should be true. An agnostic is in the same boat as the deist; they need to give a reason why the door should be even left open for the last statement, if it does not need to be left open to the first two. To my knowledge, no one has done this yet. As for the first two propositions (the asteroid and the ostrich), there is far less disagreement.

Posted: Mon - July 31, 2006 at 10:07 PM | | | |

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