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I still fail to see how one can make any assertions about the probability of life on other planets without some knowledge about the probability of life on other planets, which is a tautology

They are my beliefs, and I base my beliefs on the shear size of the universe and the material in the universe, consisting of trillions of suns, vast island galaxies of stars with millions of planets orbiting billions of stars systems. I have heard estimates that there are probably a million stars for every single grain of sand on Earth.

No offense but If you had lived hundreds of years ago, I am confident you would have been one of the people that believed the Earth was flat because there was nothing known about the size or shape of the Earth, therefore, it must be flat, or maybe when the sun was eclipsed, you would have thought the sun was being eaten by the sun monster.

I am going to risk the lable of practicing tautology again, by saying, yes, it is possible that no other life exists outside of the microscopic, tiny object we call Earth, but I would seriously doubt it. Try and open your mind a little and dwell on the size of the Galaxy, which is microscopic compared to the Universe. Try to imagine a piece of string with only one end. The Human mind will have difficulty with that image. The vast size of the Universe is beyond Human imagination. Lots can happen outside our little home called Earth.

No offense but If you had lived hundreds of years ago, I am confident you would have been one of the people that believed the Earth was flat because there was nothing known about the size or shape of the Earth, therefore, it must be flat

No offense taken, because you're wrong. I would have indeed said there was at that time no evidence (known) that the Earth were round, however I would not have made the conclusion that therefore it must not be round. I would have withheld my conclusion until some empirical evidence was had. Please note I have not made any assertions about life in our universe, I simply see no reason to believe that life exists anywhere but on Earth. Pointing to the vastness of the universe says nothing whatsoever about the probability of life existing elsewhere.

I am going to risk the lable of practicing tautology again, by saying, yes, it is possible that no other life exists outside of the microscopic, tiny object we call Earth, but I would seriously doubt it.

And again, I'd ask why you doubt it. What is that doubt based upon? Again, I'd point to the *fact* that the vastness of the universe says absolutely nothing about the probability of life existing elsewhere but on Earth.

IF we were to demonstrate that abiogenesis is possible, which we have not (in fact every attempt has failed miserably), then we would have the first bit of evidence. We would still need to then determine what precursors are necessary for said abiogenesis, and then after that we would need to determine the ratio of planets with these precursors to planets without these precursors based on a sample of known planets, and then after that we would need to determine the probability of abiogenesis occuring once the needed precursors were in place. None of these things has been done, and many people, such as myself, suspect they never will be done. I for one, do not believe abiogenesis can occur. Life from non-living matter is, in my humble opinion, not possible. When and if it is shown otherwise, I will update my belief. Until then, we can make no assertions one way or the other about life existing anywhere else in the universe.

On the other hand, you can make the assumption of scientific naturalism and base your conclusions off of this assumption, but as I mentioned, naturalism is a scientific philosophy, not empirically verified by science with respect to biology.