[David Sklansky]

I didn't say his idea was unreasonable. And if he hadn't actually written about the concept I could give him air. But he actually THOUGHT about it and still got it wrong. All he had to do was notice a few things (dense things slow down slower, he doesn't feel his movemment much on a steadily galloping horse) and see where that logically leads and he would have realized that there is no difference between stationary objects and moving unaccelerating objects. Incredibly smart people would realize these things. Newton certainly would have even back then.
And your comment about Newton missing relativety is wrong, because he did not know the results of the Michaelson Morley experiment.

As for smart people not making mistakes, the fact is that when they are incredibly smart and have thought about something hard enough to merit putting it on paper, their mistakes are so much rarer than less smart people that when confronted with a mistake like this, Baye's Theorem tells us that the much more plausible explanation is that he wasn't incredibly brilliant rather than he was and made a very rare error.