For example, among rationalists, it's probably trivial to say that any given partner is very unlikely to be the best possible. That's really simple statistical inference. But to say that in other contexts signals that you are at best, a misanthrope, and at worst, Pure Evil.
Consider the secretary problem. One can argue that someone good enough that got selected is essentially best possible.
After being employed for a while, the secretary might become the best secretary possible by being familiar with the employer's habits and such.
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