THB: Extraterrestrial life exists

To begin I have to comment on the notion of the question for debate once again. The points that were made by my opponent during Round 2 of the debates does have some very good points pertaining to the idea that alien life could exist, but once again the question remains unanswered. The mathematics have shown through my opponents calculations that it is very unlikely for aliens to not exist, but this still leaves an area of disagreement, with the maths still showing that it is entirely within the realm of possibility that no alien life exists anywhere beyond our realm of knowledge. This means that overall your argument does make the clear point that alien life is very likely to exist, but this does not support your claim that it does, beyond any reason of a doubt exist, as there is still an area of your argument which clearly states that no alien life could exist whatsoever. Just because something it is extremely likely to be true, does not mean that it has to be true as a result. Improbability does not imply impossibility. Meaning that just because it is very improbable that there is not life anywhere else, it is not impossible that we may be the only intelligent beings in the universe. Your argument is indeed good and very thought provoking, but it cannot justify beyond reason of a doubt your claim in the belief that alien life exists. On to your next point of rebuttal. You claim that my points are refutation to ideas that you had never put forward, which is true to some extent. Within your round two argument you never stated that these forms of evidence were proof of the existence of alien life. However, these points make a very relevant comment on the ideas that you put forward. All of the ideas of cave paintings, eye witness testimony and video footage are suggested physical evidence for the existence of extraterrestrial life. However, in your round 2 argument, you put forward no evidence whatsoever. Your entire summation of your argument says that "The Universe is so extremely large and has existed for such an extremely long time. that the probability of extraterrestrial life is so extremely high that it is difficult to comprehend". You summarise your whole argument based on the concept of likelihood of an event. As I stated earlier in this rebuttal, just because something is improbable, does not mean that it is impossible. This idea can not only be applied here, but it can be applied to every day life. Using mathematics I could make a wide range of statements to show that something is very likely. Mathematics based around my health, the area where I live and other factors could show to a very high degree of probability that I will survive the next hour coming, but I cannot say that this has to be true because the probability of me dying is so extremely low that it cannot be comprehended. You make the claim that I use the absence of evidence as an argument that they don't exist, to some extent I do, but there is a level of a similar action here, with my opponent stating that because the probability of there being extraterrestrial life is so high that we cannot comprehend it, this means that there is strong support for the claim that it exists, which I am afraid to say there is not. Now referring to your claim of multi-cellular organisms. In your opening statement you made reference to the biological concept of MRS GREN, a system of seven criteria to determine whether something is in fact a living organism. Now pertaining to your idea of these being alive, yes they could be according to this idea but this is only one concept of what it actually means to be alive. In order to answer this we must look into basic philosophy and see whether it is classed as alive based on these ideas, as there is a very big contrast over whether these cells can be classified as alive. There is a big debate largely surrounding abortion (which is a debate for another time), in which some argue that a fetus is not alive until some weeks into the pregnancy, despite the fetus being a collection of cells at this point. To have something be 100% true it must be proved beyond reason of a doubt and to see that there is still clear debate amongst people as to whether it is alive, this idea of MRS GREN must be postponed until there is a common agreement about the human interpretation of when something is alive and when it is not. As such it is hard to say with 100% clarity that any bacteria or other cellular level organisms in space can be counted as clear evidence for life when there is this widespread disagreement. This means that our debate is restricted to this concept of humanoid and sentient beings at this point in time. You also use the ALH-84001 meteorite found in Antarctica as an example of evidence that points to there being alien life. Now when first discovered the researchers believed there to be evidence of bacterial fossils from mars on the rock, but these were very controversial claims, and in fact, the wider scientific community rejected these claims after further study of the meteorite, making it completely redundant as evidence of anything other than a meteorite that has fallen to earth. Now there is this common theme amongst believers in extraterrestrials to say, there is evidence, you just haven't looked closely enough, as said in a much more polite and professional way by my opponent here than by many others I have had this debate with. I did some research around cases similar to the meteorite in which you spoke of and all of the evidence that has been used by my opponent's side of the debate all share an extremely common theme. They are all controversial. Not a single piece of evidence found can say to a great level of certainty that it is evidence of alien life. The meteorite was argued against by the scientific community, the Wow signal has not be proven to be of alien origin, mars landers have not been able to gather the same results as the Viking lander which apparently gathered evidence of bacterial life in the soil. There is not one single piece of credible evidence that points to alien life existing as of current. This spawns another debate question of, if alien life cannot be proven to exist, does it belong in the realm of science, or should it be paired with more philosophical concepts such as the ideas spread by religions. Now my opponent says that if we were to imagine life on a small world orbiting a star beyond our range of detection, that the life would exist but we couldn't detect it. Now this is a very common argument and it is one that is hard to debate against because it is almost an unanswerable question, similarly again to the way in which religious people argue that we cannot find evidence for God because it is beyond human detection and comprehension. This is not a supporting claim for extraterrestrial life existing. It is not evidence or scientific reasoning to say that something exists purely because we have not found it yet. On the contrary it is much more reasonable to say that we have looked for evidence of this object and we cannot find it, meaning therefore that we can conclude that object x cannot exist. Whilst it may be true to say that an absence of evidence is not an evidence of absence, it is more logical and reasonable of an argument, than saying object x is likely to exist, we have found no concrete evidence of object x, but this is simply because our science is not good enough to find it yet. If our science is not good enough to find evidence for your claims, then you have no possible realm of evidence to support your claims. We come to your rebuttal about my statement, to justify any claim you need evidence. You say that there exists a priori, a statement that does not need to be supported with factual evidence to know it to be true. Now this is true in today's society, it is fair to reason that "all bachelors are unmarried" because this is something that we know to be true. However, my opponent ignores the clear evidence behind each component of that claim that has led us to be able to say that without evidence. We had to define the term bachelor looking at people in our society who were unmarried and have never been married in their lives. In order to give them this title we had to observe the actions and behaviors of individuals and be able to conclude that scientifically, all bachelors are unmarried. Without having previously observed and defined this term using reasoning, this would not be a priori. Now this concept is very similar in science, known as a paradigm. Paradigms are a set of shared assumptions and agreed methods within a certain discipline. However, just because something is widely accepted to be true, does not mean that it is. Paradigm shifts often occur in science that lead shared assumptions to change. Early in human science, it was believed by scientists everywhere that everything orbited around the Earth. After further research this assumption changed to the now universally accepted idea that everything orbits around the sun, after concrete evidence proved it beyond reason of a doubt. Up until the work of Charles Darwin, everyone believed, in science, that man was created by God in his image. The work of Darwin and other scientists has proven, beyond reason of a doubt using evidence, that we evolved over a very long period of time. All widely accepted assumptions are based on some form of observable evidence. This means that my use of the phrase"to justify any claim you need evidence" is in fact true in the realm of science, the only field which could possibly provide clear evidence of alien life, which it has proved, beyond any reason of a doubt, that it cannot do. Your probabilistic claims do not need to be backed by empiricism, but this does not make them fact, they are simple estimates that cannot be used to prove anything. Pro has failed to prove beyond reason of a doubt that her claims are true, meaning that they cannot be taken as fact.