Applying Pascal’s wager we should believe him (in Pascal’s case, the case of God, the consequences are infinite after all …).
Or, applying the Scientific Method; and asserting that we have no undeniable information, then the odds depend on the probability density we chose. But we have no information on the distribution either. So let’s assume Gaussian\Normal probability density distribution by the Central Limit Theorem. (Although my intuition, illogically, likes the Uniform Distribution). In any case, our guess should be the first moment, i.e. the mean of the distribution.
It is improbable that we are alone. In other words a probability of zero is, well, improbable …
Once we assume one alien species, there are probably others …
However, there is no reason to assume they exist on the same size scale as us.
To me, again just on intuition, they probably exist both in today’s space (i.e. our space-time cone in the sense of General Relativity) and over all time and space (past and future), so the question may be why are the hiding from us. Or are they herding us … or ..
So back to the interview
Is he sincere, i.e. believe what he is saying? Probably?
Or does he have an ulterior motive? Selling a book? Attention? Well yes.
Or is he deluded/instance? Well ..
Well what is the probability…?