[mellosouls]

Talking of the extreme case of life being unique to earth seems unnecessary; there can't be many people outside of some fundamentalist niches that hold that view.

More generally on the subject considered seriously, without taking into account the various factors involved in predicting the probability of life it is unwise to talk of certainty and scoff at sceptics of its abundance.

There is also an important distinction to be made between life in its simplest form and at its apex; it is the latter that perhaps most people think of when looking upwards in wonder, and there is no reason to think that the distribution of intelligent life is such that we have good chances of contact and interaction, however we may wish it to be so.