[dthunt]

It's actually not a problem. You can come up with any number of hypotheses about coins. Some of them take the form, "This coin will produce <some specific output> in the next 1000 typical flips". That hypothesis and others with similar, more complex form, like the pair of hypotheses that predict flip 1001 after the same first 1000, GAIN CREDENCE when you perform 1000 flips that conform to them. Others of the similar form lose it. Other hypotheses of wildly different construction, like, that a coin is more or less fair, lose and gain credence according to whether or not they predict the observed result.

The fact that you didn't write a hypothesis down before you did the test has very little to do with whether or not the data supports the hypothesis. Hindsight bias matters, but only as far as it corrupts your experience. The machine with the infinite library of coin-flip-hypotheses updates just fine.

On a side note, coins are not fair, in general, and Jaynes actually goes into some detail about the process of cheating at coin flips.