Technical term for an assumption about probabilities?

Question

There is a term of art that I either never learned or forgot, referring to an assumption in the context of estimating probabilities. I cannot find it in a quick search of Wiki on, for example, the Drake equation, which is the sort of speculative estimate I'm thinking of.

The term (if there is one) refers to the intuitively reasonable but unprovable assumption that an event which has occurred was more likely than not to do so, meaning, at a minimum, not highly unlikely. For example, if I assume that because earth has a good climate for supporting life, and since life arose on earth, then life is "quite likely" to arise given good conditions, does that general category of assumption have a name?

Answer 1

This is different to what you are describing, but perhaps you are thinking of the anthropic principle? This principle holds that all observations must be consistent with the existence of a conscious intelligent observer (to make those observations), and therefore all probabilistic inferences must condition on this fact. This implies that it is unremarkable that the Earth has highly-tuned conditions for life, since if it did not, there would be no living observer here to have noticed this. Another way to think of this is that the probability that our home planet has the conditions to sustain life is one, since this probability must be assessed conditional on our existence and ability to observe it.