As the scientist considers the basics of scientific theory, such as the origin of the universe and also the origin of life on Earth, he's left with the problem or probability.
Science relies, essentially, on predictabilities: what are the variables in a chain of events which permit one to predict a specific outcome?
The problem with theories addressing the origin of the universe and the origin of life on Earth is that no one knows the variables required to calculate the probabilities; nobody knows causality for either theory. Being the scientist takes these theories into consideration, any credibility he ascribes to them may be a matter of faith.
That's to say; in the absence of causality, any explanation is simply based on assumptions. There's no distinction between a belief in the big bang and a belief in a creator, and, likewise, there's no difference between a belief in abiogenesis and a belief in a god breathing into the nostrils of Man.
Left with the reality of not knowing however rather believing, Man is obliged to indicate a degree of humility in speaking on the origin of the universe or the origin of life on Earth. Both religious and scientific men typically express their beliefs in a dogmatic manner.
I have never heard anyone arguing, passionately, over the existence of Pluto, despite the fact that he has yet to see it with the naked eye; he, for the most part, trusts the scientific instruments that have made it known to him, however on those things of which people have no objective knowledge, like the origin of the world and the origin of life on Earth, people have died.
Life (corporeal life) has either existed for all eternity, or it has not. If it has, we are faced with the infinite regression problem. Thus, to my mind, there's no alternative to abiogenesis.
We are the proof. Note: this doesn't address the question of whether or not we came about through some unknown interaction of environmental conditions and chemistry, or whether God created us from the dust of the earth. In either case, it's abiogenesis.
