given the sheer size of the universe, the most reasonable view is expecting that alien life exists

Before I get into this, I'm going to nail some things down...Alien - Definition: Extraterrestrial.Life -This is going to be looked at in the way that most reasonable people would understand it.Exist - Definition: To have life.Examples of things that are alive: Animals, humans, and plants.I'm going to specifically exclude all forms of deities, space, stars, and energy based life (including dark energy), otherwise the debate becomes ridiculous. Also, life must have some mass, and therefore matter.Sheer -Definition: Nothing other than; neither more nor less than; that and nothing else. This is a pretty standard,denotative meaning.Size -Definition: Volume.Universe -When talking about the universe, we will be talking, specifically, about the observable universe.Restating the issue: Given nothing other than the volume of the universe, the most reasonable view is expect that extraterrestrial life exists.Not Enough Information:Given only the volume of the universe, we don't even know if there is matter in the universe. Therefore, we have no possible way of knowing if life even exists, let alone it being reasonable.Even if we use the current estimates for volume and critical density of the universe, we still have no reason to believe that there is life, or any sort of structure. We were not given the idea of physics, and therefore know nothing about gravity. So, for all we know, the universe could have all mass evenly distributed; this would leave us with roughly 1 proton per 4 cubic meters (1). Those are unreasonable conditions for any form of life.In short, we have nowhere near the amount of information required to determine that there is life, let alone find it reasonable to expect alien life to exist.Fermi's Paradox:"The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist.However, this hypothesis seems inconsistent with the lack of observational evidence to support it." (2)I wanted to formally mention this, as it is an important issue.To be fair, you did start to address it, but you really only stated that alien life could be too far apart in time, or too far away, distance wise.Being too far apart in time doesn't do anything for your argument, seeing if the alien life is dead, it no longer exists (which you already mentioned).If the distance was an issue, then we should have observed alien life that ceases to exist. Granted, that presupposes that intelligent alien life existed long before terrestrial life, but you already stated that it could have. If we saw any observable evidence that confirms there was alien life, then Fermi's paradox wouldn't be an issue.Habitable Zone:The habitable zone is the zone in which it is theoretically possible for the planet to have liquid water on its surface. (3)Basically, we can use this to get a more accurate number for possible planets life can be sustained on. Although, it has been suggested that life can be sustained elsewhere, the most 'certain' would be an article that basically says that it is theoretically possible, but it's not very practical. (4)Anyway, there isn't much data or very many sources I can find that even attempts to guess the number of planets in the habitable zone for the entire universe, but there are some figures for our galaxy. One of the most recent set of articles was based off NASA's Kepler mission, which extrapolated the data and came up with a total of 50 billion planets, in our galaxy, and only 500 million reside in the habitable zone. (5)Armed with that information, we can do more accurate calculations. But, we still need a little more information...There are approximately 6 x 10 ^ 22 stars (6), so if we assume that our galaxy is representative of the universe (which is highly unlikely) we can at least get some sort of approximation...In our galaxy, there are around 170 billion stars. (6) This makes the ratio of habitable planets to stars approximately 0.00294.Now, if we multiply that by the number of stars in the universe, and divide by the completely arbitrary number you decided, we get around 176,470 planets with life. Now, we've made gigantic assumptions, and it is in no way close to statistically significant, even if we account for significant figures... I should note, that 176,000 is far from the 49 million, which again, is entirely based on some arbitrary factor of 1 quadrillion, and numbers that vary wildly.Conclusion:Given only the size of the universe, which is all that was given, we have absolutely no way to determine if there is life, let alone determine that the most reasonable view is to expect alien life to exist. In addition, Fermi's paradox has not been resolved, and there no statistical evidence that supports the idea that alien life exists.(1) http://map.gsfc.nasa.gov...(2) http://en.wikipedia.org...(3) http://en.wikipedia.org...(4) http://www.pbs.org...(5) http://www.space.com...(6) http://iopscience.iop.org...