Yes, thank you. It gives me one idea, at least.

The usual argument against parasitic tension probably applies to thinking. If your body is holding unnecessary stress, and doing unnecessary things (particularly in the brain, as opposed to spinal reflexes), then there is good reason to believe that this would hamper learning, in terms of sapping energy and attention. There probably are more and less effectively body activations for learning.

But I wonder about the fundamental claim here, though, about what we "must know" in order to think. Does he cite evidence for these claims?

I expect that your nervous system is always adapting to the local gravitational field, and the effects it has on your body, but in what sense "must" you know where you are, and in what position? What happens if you don't?