Yes, there are some known knowns, and they aren’t going to change
One of the most spectacular statements in my lifetime was uttered by Secretary of Defense Donald Rumsfeld in response to the lack of evidence for Iraqi WMDs in 2002. The core of his response was…
…as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don’t know we don’t know.
My interest here is not in the Iraqi war controversy, but in the more general idea that there are, in fact, “known knowns…things we know we know.”
Last night I had a very enjoyable barroom discussion with two smart colleagues about the possibility of immortality and the existence of the human soul. Both of my friends thought such things were at least possible. I took the contrary position, based largely on physicist Sean B. Carroll’s assertion that the laws of physics underlying everyday life are completely understood, and that immaterial souls, if they existed, would necessitate a complete overturning of that understanding.
We know the equation that makes everything happen at the level at which we exist. Souls/spirits would need to interact with that existence by some mechanism, since in their usual conception they are able to access and retain information from the brain of the person with whom they are associated. But the standard model that explains all of our existence has nowhere for that interaction to occur.
After explaining this, the inevitable happened. One of my two friends pulled back to the “unknown unknowns” Rumsfeld defense. This is the all-too-common fallback when someone making an extraordinary claim is asked to prove it. In this case, it presented as “science doesn’t know everything, and things science used to claim to know are overturned all the time.”
What’s wrong with the unknown unknowns defense?
- We can’t know anything about an unknown unknown, so it serves no useful purpose. To use Bertrand Russell’s famous illustration, we can’t know for sure whether or not there is a teapot in orbit between Earth and Mars, so asserting that there is, is no argument in favor of such a teapot. So asserting that there are things that science does not yet know (undeniably true) is not an argument in favor of anything (including the existence of immortal souls).
- It is a fallacy that anything and everything science asserts is equally likely to be overturned someday. We often hear this illustrated with examples from things like weight loss or dietary health, where something thought effective a decade ago is now said to be ineffective, or vice versa. But that is a false equivalency between the particular and the general. At the particular level, falsification is the way science works, and how science makes progress, creeping ever closer to the truth. But at the general level, there are indeed known knowns; things about which our degree of certainty is now so high, they are for all practical purposes, incontrovertible.
- Evolution and the standard model of physics are examples of “known knowns.” They are always subject to new discoveries and corrections in their particulars, but the general theories so completely and faithfully predict what happens in the real world, that the probability they are wrong approaches zero.
So the problem with immaterial, immortal souls is that they would require the total overturning of one of our fundamental known knowns. They could certainly exist (at least in theory) as something wholly apart from our existence. But in almost every conception of souls, certainly all those posited by religions, the souls are required to have some interaction with this physical world.
It’s at that point that they become virtually impossible. And so those who want to believe in such things inevitably fall into the black hole of the unknown unknowns defense.
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