it is more probable that aliens exist than not

Statistically Impossible: I still do not know what this term means. Pro restated the point that the non existence of life on other planets is statistically impossible, but did not define this phrase. I believe any probability above zero, no matter how small, is statistically possible. Pro can win this one without the use of statistical impossibilities so I recommend he either defines statistical impossibility or drops it altogether. I am not sure any event is "statistically impossible" when dealing infinity and so on, but I think Pro may be saying the likelihood of life not occurring on other planets, given the large number of planets in the universe, is so little as to function as zero probability. This discussion arose on a math Q/A on the web. . http://mathforum.org... Not the best stuff, but I see no need to ruin a debate by spewing "lies, damn lies, and statistics". Pro is positing this position: 1. Given that life arises by natural processes 2. Natural processes occur in all parts of the universe 3. Given the large number of planets/moons, etc. 4. Natural processes are more likely to form life on other planets as opposed to not. I recommend leaving "statistically impossible" out of the debate altogether. Rebuttal: Fact-we don't know how life arose on our planet. We are getting closer, but we are still missing vital parts of the explanation. We cannot say what the probability of life on other planets would be, until we understand what conditions are necessary for life to form. I fully agree that if life occurs on other planets then we can say the organisms probably evolve as we have a robust theory of evolution, but the formation of life itself is still beyond our understanding. Pro needs to show how we can determine the likelihood of an event (as he declared the event [life formation] as being "more likely") when we do not understand the event itself. Such a conclusion is without warrant. Trillions of Planets, Goldilocks zones, and Uncertainty: I agree we have more planets in the universe than we can count right now, but I also agree that no two planets/moons are identical. . http://news.vanderbilt.edu... (This example deals with binary stars) This should not surprise us as we know that random events such as meteor strikes affect the current state of planets depending on when they get hit, the size of the strike, etc. What are all the elements needed for life to form? We do not know yet. What particular "earthlike" aspect should we be looking for to find life? We do not know yet. Given that differences exist between all planets/moons and celestial bodies in general, what basis do we have to support a higher likelihood assessment that any planet other than our own can accommodate life given its differences? Not much. For voters, a Goldilocks zone is defined as a zone which allows a planet to have surface water. . http://en.wikipedia.org... As for life, the assumption needed for these planets to be considered more viable for "earth like" life is that surface water is necessary for life formation. This is a good assumption, but given the numerous unknowns in abiogenesis, we cannot say what earth like feature is the best to produce life. Surface water is a good start, but surface water is not the only factor, nor do we know if it the most important at this point. Given the large number of uncertainties concerning abiogenesis, I conclude that claiming a more/less likelihood of life formation on other planets, at this point in our knowledge, is unwarranted. My opponent presented information concerning abiogenesis and this is not necessary as I stipulated that life can arise by natural processes. He did err in suggesting the "primordial soup" is widely accepted. . http://en.wikipedia.org... The deep sea vent concept is making a good show right now. . http://www.livescience.com... I fully agree that life arises by natural processes and, as of yet, we do not know what those processes are so we cannot claim with much accuracy the likelihood of life on other planets until we know more about it. As much fun as the intelligent being idea presented by my opponent may be, it is not relevant to this debate. Pro has not made his case; therefore, he has not met his burden in this debate.