[RadioAstronomer]

But Occam's Razor indicates that the simplest explanation - that we are the only ones - is the best working theory

Are you sure that is the simplest explanation?

[thoughtomator]

The simplest explanation, I would suppose, is that we are simply ignorant and don't know. But that doesn't help at all in the search for truth, does it? Not being content not to know, theories must be proposed and examined to determine what is and is not truth.