Life is not improbable.

[Heywood]

The probability that life (as we know it) will evolve is 1.

Really? Is there such a thing as a priori probability being 1?

I'm using a definition for evolution here which is rather loose or broad......Basically I am thinking that evolution is just descent with change.

But you are correct, it isn't 1 because over any time specified time scale I suppose there is a probability that life as we know it can occur were there is descent but no change.

Thanks for prompting the thought.