No one can discuss the origin of life or even the origin of the universe, that is impossible.
It is arguably accurate that we cannot discuss the origin of the universe since it means talking about what happened before time.
But as to the origin of life we actually
can discuss it and indeed investigations can move us toward a reasonable hypothesis.
The evolution of life is a speculative attempt at explaining the history of life on this planet.
But the chemistry was already in place for about 9 billion years before the earth began, so once we form the earth, cool it, get it to the point where we can utilize the chemistry we can wind up with life.
There's a lot of interesting and valid data on abiogenesis and there is no reason to assume we can't possibly every understand how life arose.
We rely on a partial fossil, a record of only certain life forms for this purpose, yet there is far too much missing in the fossil record.
There is a lot missing in the fossil record, but the fact of the matter is
there's a LOT OF INFORMATION THERE. Enough to give us a huge amount of information on evolution and how life has changed over time. It's like seeing a movie but at a much longer frame rate with a few frames missing.
To arrive at any satisfactory theory, we must fill in the blanks, assume this and that, except perhaps for those prone to wishful thinking.
That isn't really how it works. Indeed we would love to have all the data available. Every scientist would. But that isn't always possible. In the case of the earth sciences and even biology there are things that may be missing. Sometimes we know they're missing and we can utilize that lack of information to understand what is going on.
Think of the fossil record as a
random sample of life's forms. We don't need to see every single brachiopod in a Mississippian Formation to be able to draw significant conclusions on
brachiopoda in the Mississippian. So much of science is done using SAMPLES rather than entire POPULATIONS. And it's all just fine.