It is about relative probabilities.
We're agreed on that fairly indisputable point, then. You didn't actually address the point that whether something is possible in the first place isn't relevant to questions of relative probability, unless one or both is simply impossible. Given that your overall argument looks like it has been little more than 'Both are possible, therefore, they should be treated as equally probable,' that's a very real issue that you need to address.
No, our existence doesn't make alien life physically possible. It only makes Earth-based life physically possible. If this is the only planet in the universe where the conditions are right for life, then alien life is physically impossible- there would be no place for it to occur, other than here.
That point had actually been addressed, if you were paying attention to the whole post. For the record, normally, throwing out "physically possible" is used for referring to the general underlying rules, rather than specific potential situations. Physically possible does not mean that something actually is the case, after all. Simply stating a specific case is usually done directly. In short, that we exist demonstrates that the underlying rules make it "physically possible," but does not indicate specifically that it actually is the case. This is in contrast to ESP, which we don't even have remotely solid evidence that it's "physically possible," at last check, before getting to anything after that. That alone tips the balance towards advanced alien life being more probable than ESP rather significantly, before touching other things, such as that we don't even remotely have the resources to check all the places where advanced alien life could be and have barely begun to get the relevant data needed to make anything close to an accurate assessment of the actual probabilities, whereas ESP has been tested rather extensively in relevant ways and overwhelmingly failed to distinguish itself from the alternate explanations.
You're simply asserting that.
I can do likewise.
Indeed, you can try to assert differently. My statement was conservative, regardless, though, and isn't actually contradicted by yours, in fair part because many of the probabilities that might be more likely to be limiting there are simply unknown, and your argument still has little weight when it comes to the relative probabilities, given that ESP hasn't overcome the basic hurdle of demonstrating that it's physically possible in the first place. Yes, dealing with the general rules, rather than specific potential exceptions.
Is a Jupiter sized planet a necessary condition for life? Is an axial tilt? If so, how much? A large moon, relative to the size of the planet? If so, how large? How far away can the planet be from the star? Neither of us knows. The rare Earth hypothesis may or may not be true. It's impossible to disprove, until we actually discover alien life.
And isn't necessarily disproved even if advanced alien life is found. Either way, "neither of us knows" is a dangerous line of argument to engage in when there's easily accessible information about things like the
Goldilocks Zone, for the form of life that we're rather familiar with, alone.
But "planetary habitability" would probably be a better term.
If you're simply dealing with life, perhaps, keeping in mind that habitability deals with how suited a planet is for life, not whether there is any there or how likely it is to have come to be there.
If we discover abiogenesis is so unlikely that the odds of it happening anywhere but here are a trillion to one, for all intents and purposes, alien life will be physically impossible. But you're right, it would still be theoretically possible, but no one would believe in it, which was the point I was making.
Maybe. That does depend a bit on how accurate those odds actually are, though, and ignores that many people tend not to be entirely rational about their beliefs. Either way, the good part about your argument here is that it's potentially relevant to the question. The downside of it is that it's currently mostly empty speculation and that it's already past where ESP is. When the first major hurdle that needs to be overcome for ESP is demonstrating that it has any actual basis in reality, while advanced life has already passed that hurdle, they're not on even grounds when it comes to how probable they are at all, contrary to your arguments.
There are no solid reasons why alien life should exist, either. We would have to know what the necessary conditions for life are. That is unknown. We know the conditions here are sufficient, but we don't know which ones are necessary. If there are many necessary conditions, then the odds drop accordingly. Like you said, there's no reason to think there are a lot of necessary conditions, but there's also no reason to think there are only a few. Without knowing what the necessary conditions are, the odds are impossible to determine.
The number of planets in the universe only helps if we're able to figure out what the odds of life arising on other planets is. Those odds are unknown. They could be 1 in 50 or 1 in a number higher than the number of planets in the known universe.
You're missing the point made there in the contrast, rather blatantly. In general comparisons of probability, think about which of these features can be considered to indicate that something is more probable than the other: "We know it could be the case, given precedent" vs "We don't know that it could be the case, given lack of known actual precedent or valid mechanism," and "We don't have solid reason to conclude much about how likely it actually is, given lack of relevant data" vs "We have solid reason to believe that it is extremely unlikely, based on quite a bit of relevant data, even if absolute proof that it is not the case is fundamentally impossible."
ETA: Your post was well thought out, and much appreciated.
Thank you.
Where is the proof that numbers exist?
