Re: Note on Sagan
You seem to be somewhat confused, and you are ignoring the logic of reasoning.
1. From a philosophical standpoint, believing does not enter into the equasion. My comment is about proof.
2. From a scientific standpoint, you believe someting to be the case, you can go about proving it.
In your case of oxygen, proving or disproving oxygen is toxic is proof in both cases. What Sagan seems to be postulating (from what I read about the man, I never met him) is that absence of proof of non-existance is proof of existance. This is pertinently untrue.
Again, this is not a matter of belief. It is cold hard logic. In the case of the existance of god, the fact that there is no(t yet) a unyfying theory of evolution in it's broadest sense does not equal proof of the existance of a deity.
I am sorry I can not make this clearer to you in a forum post, and I wil therefor shut up about the matter.
You may, of course, believe what you like.