Thats just it though, we use math to quantify the chances of life evolving elsewhere and use that to make an intelligent guess, which is all that it is.
...but its more than just a guess....these numbers are often used as evidence, such as "there are too many stars and we're discovering planets every week, so there simply has to be life out there".
You want to know what is truly arrogant, the belief that this vast universe was built just for us.
For the record, I don't think the Universe was built for us...I just think Earth was since radiation-bathed space is deadly and inhospitable.
There are (best guess) 10,000,000,000,000,000,000,000,000 (someone please check my math but if its off it is to low) "solar systems" in the Universe and that is just from the galaxies that we can see. The number could easily be many magnitudes higher. If you really want to twist your mind, since the light that we see from those stars is millions/billions of years old perhaps that number is far less due to the stars dying.
No disrespect, but so what? That isn't evidence. This sounds like a faith-based assumption.
To believe that all of that was created for such a primitive species such as ours (relatively speaking) is beyond arrogant.
I agree, that's why I only believe the earth was created for "us". I personally believe the rest of the cosmos are just evidence of a creator with unimaginable power.