January 21, 2015

Difficulty Explaining Something is Not Useful Evidence

German garden gnome
By Colibri1968 at en.wikipedia [Public domain], from Wikimedia Commons
Suppose I planted a small vegetable garden in a corner of my yard. In spite of my lack of any real gardening ability, it is coming along well. Everything is growing as it is supposed to, and I am thrilled that I will soon have fresh vegetables. But then disaster strikes. I go out one Saturday morning to do some weeding and discover that something has been digging up my garden. Some of the plants have been completely uprooted. I repair the damage the best I can, but it keeps happening. I consult with the staff of the local garden store and try a variety of solutions they recommend, ranging from a small chicken wire fence around the perimeter of the garden to various chemical compounds supposed to safely repel rodents and other small animals. Nothing works.

What is digging up my garden? Suppose I were to tell you that I believe the culprit is some sort of magic gnome. After you were finished laughing, you'd inquire about my evidence for such an implausible scenario. "I've got plenty of evidence," I tell you, "just look at my garden!" I remind you that my garden is being dug up every few days. I list off the various solutions I have tried, all of which has been ineffective. I remind you that nobody has been able to explain what is causing the damage. "You see, it has to be a gnome."

The mistake I am making here should be obvious. At least, I really hope it is obvious. I do not know what is digging up my garden, and I am trying to use my ignorance here as evidence in support of my gnome belief. But this is not how evidence works. The fact that I don't know what is digging up my garden is not only insufficient to support my gnome belief; it isn't even particularly useful evidence. The fact that I can't explain what is happening has no bearing on the possibility that a destructive gnome is responsible. I might as well claim that gods are destroying my garden.

Wait a second! Doesn't this make me sound like a "pseudo skeptic" or a "hyperskeptic" of some sort? If my understanding of the meaning of either of these terms is correct, I don't think it does. Again, this is not how evidence works. My inability to explain a phenomenon is not evidence supporting the existence of some sort of entity (e.g., gnomes, aliens, gods).

But if I don't assume that gnomes are real, doesn't it sound like I've already made up my mind and that I am refusing to consider the possibility that they might? Not at all. I am happy to consider the possibility that gnomes exist, but I have no evidence that they do. If I had such evidence, it would be reasonable to believe that they do exist. Until such evidence is available, it would be irrational to believe that they exist. The key is that we understand the sort of evidence that would be sufficient to support the belief. This is skepticism; there is nothing "pseudo" or "hyper" about it.

Fine. Then what would convince me that it really was a gnome digging up my garden? That's easy. I'd need evidence sufficient to support such a belief. In the case of my garden gnome, I could imagine using a wireless IP camera to monitor my garden. There are many inexpensive models to chose from, and my garden is small enough that one would probably do the trick if I could find a spot with a good view of the garden. Suppose I did this and captured video of a gnome digging up my garden. That would be evidence supportive of my gnome belief. Such evidence could then be followed with attempts to catch the gnome, etc. Of course, I would still expect you to be skeptical if I showed you a video of a gnome digging in my garden. You'd be justified in suspecting that I might have faked it somehow. But for me, seeing the video feed from my camera would at least tell me that I was on to something and that further investigation was warranted.

Without too much difficulty, we can apply the same principles to the existence of extra-terrestrials visiting our planet, angels, demons, ghosts, or gods. The take home message is a simple one: the presence of unexplained phenomena are not useful evidence to support belief in any of these things. My inability to explain X is not sufficient evidence that Y exists. My difficulty explaining X isn't even necessarily relevant to the existence of Y. To support the existence of something, we need evidence of its existence.

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