How can we surmise that chemical evolution may lead to Earth-referenced attributes of life as if it is a universal law?
Our experience with life and intelligence is wholly Earth-referenced, yet SETI and the discipline of astrobiology assert that life-as-we-know-it is unquestionably "out there". Why? Is it a reasonable assumption that chemical evolution inevitably leads to "us-like" properties wherever conditions are "just right'? How restrictive is the notion of "just right" conditions? Wouldn't such conditions need to be EXACTLY like Earth's historical conditions in order to arrive at Earthlike outcomes?
Taken at the level of molecular organization and building up from there, the probabilities of generating a bacterium, even given Earthlike initial conditions of, say, 4 billion years ago, are beyond astronomical. A probability distribution is associated with each stage of synthesis along the evolutionary path, and these are affected, too, by ever changing and largely unpredictable externalities, such as irradiation and impacts. The outcome of these probabilities then provide the prior conditions that affect the shape of the next probability distribution. All of these compounded probabilities have been integrated over geological timescales to arrive at Earth's version of life. How could recognizably similar outcomes be extrapolated to the integrated histories of chemical synthesis taking place on other worlds?
Indeed there are huge numbers of stars and galaxies in the vast universe, and we have all been lured by the numbers game that turns the even the minutest probability into an inevitability. But we should always temper our searches for ET to that vastly smaller part of the universe that is in any way accessible to us from our own spacetime well. At some scope of distance, the search for ET crosses the boundary into cosmology with contact across times and parallel universes that are not part of the ET search.
SETI and astrobiology proffer deterministic metaphysics of inevitable life within our accessible universe as if it is science. Is it science or just wishful thinking?