Did You Ever See a U F O?

I agree that a major problem with most discussions about extraterrestrial life assume carbon based life. (...and I do understand that the fundamental elements that we are aware exist could sway towards that model).

For centuries we also believed that photosynthesis was the key to the development of life on earth, but VERY recently, we discovered chemosynthesis at the depths of the ocean where light from the sun does not penetrate.

Who's to say that, for example, silicon based life (other than silicon superconductor based artificial intelligence), or ammonia based life could develop elsewhere?