[VanillaCafe]

But why are we arbitrarily reducing the set from "life" to "sentient"? Right now, we humans are looking for _any_ other life in the galaxy.

But, when considering life, if applying the Big Alien logic, I should expect to be a single bacteria. And if not that, then, say, some insect.

But, instead, I'm a human. Or a mammal. Or a vertebrate. Any of these very fundamental descriptions of myself already put me in the SMALL group not the LARGE group when classifying the population of all life on this planet.

It feels like confirmation bias to select "vertebrate" or "mammal" to show that we are already indeed in a large group.

And indeed you can argue scientists are already applying this logic by looking for signs of simple life, say, or Mars. Or Europa. Because, that's the most likely to be found.

Maybe we should call it the Bacterial Alien Theory. Of course, it wouldn't be very controversial.

[wrsh07]

Right -- it's much more likely that alien life is not sentient.

But when we restrict our search to sentient life, here is what the statistics suggest [and as you correctly point out, that restriction is what makes this an interesting discussion].