He estimates f_l, the probability of life arising in a habitable planet, as 0.1.

Abiogenesis has never been observed to occur independently of its presumed occurrence when life started on Earth.

Given the current state of scientific knowledge on this topic, the only certain lower bound on this number is the probability of molecules in a suitable "organic soup" arranging themselves into a self-contained bacterium. And that probability is a _very_ small number.

If f_l is _very_ small, then there is no need to be pessimistic about our own long-term survival. We see no advanced alien civilisations, because there is no other life out there of any kind - the rest of the observable universe is sterile.