An octopus is now an alien and they probably can start predicting who will win the world cup. — TimeLine
I'm confused as the OP did not mention panspermia let along tardigrades and octopuses.
If that is your specific concern here - you haven't mentioned a specific criticism of the OP - then that should have been stated in your expression of moderatorly discomfort. You could have just called Wayfarer out for doing his usual thing of introducing panspermia into the conversation at every opportunity and, more especially, asked him to source his comments about tardigrades and octopuses (but only if you wanted to encourage him to derail the OP - a reason I passed over it in silence).
Panspermia research does offer the evidence of extremophiles like tardigrades. But talk about octopuses being alien is - as far as I can see - just a meme. Wayfarer might be able to show to the contrary that it is part of panspermia as a serious hypothesis. So if you were really looking to draw some line, tardigrades would be some kind of accepted science, octopus become the lunatic fringe.
So you are attempting to justify drawing a boundary line in terms of hyperbole - "An octopus is now an alien and they probably can start predicting who will win the world cup." But hyperbole is a rhetorical device and not a suitable method for the drawing of fine distinctions. If you defend your position, as you have, with hyperbolic statements, then that is a bigger failure in critical thinking than the one you meant to criticise.
I do respectfully agree and reiterate that I will certainly be cautious before ever making a decision otherwise, but my intention really was to understand whether this subject could indeed be considered Philosophy of Science and not about moderating risks and what not. — TimeLine
Cool. But again the OP seems utterly unproblematic in that light. It sets out a chain of reasoning in full. It asks a question that is worth answering - on moral grounds, if we are going to cart our bugs to Mars, if nothing else.
It contained a "scientific error" at the last step, in my opinion. The OP assumed that our immune system has to be evolved to recognise invasive biological threats. But we now know our immune system instead can learn because it generates a variety of antibodies on a "just in case" basis. It doesn't know what might be coming down the pipe, so it produces a range of receptors and uses these to discover what might be "alien" in terms of what it knows to be not "the usual biology out which 'I' am constructed".
So, my point is, even if we found an Earth like world - with similar gravity, atmospheric composition etc - this similarly is only superficial - and its biosphere - especially life at the microbial level - would make moving and colonising this planet impossible - unless we develop immunity to its biosphere as we have done here on Earth. — JohnLocke
So - given the OP's constraints around this other planet having a very Earth-like chemistry in other respects - it is reasonably unlikely that alien life would escape detection by our immune system, especially if the life was biologically similar enough to be infective. And even just being an unrecognised organic chemistry would be enough to set off an allergic reaction.
But because our immune system learns, then it is possible we could adjust in months rather than millions of years.
Thus the OP asks a completely reasonable question - one that is speculative and yet also one we can start to make more precise sense of; break it down into more specific questions to be answered.
Wayfarer of course went off at a tangent. The idea that octopuses could be aliens in our midst is a risible hypothesis with little to no scientific motivation.
If Wayfarer thinks something he read somewhere does provide proper motivation, he can cite the source. He would need to present a similar careful chain of reasoning that leads towards some central well-focused question - a question that would have maximum impact on the holding of the theory outlined.
And then even a risible hypothesis is meat for philosophy of science. Learning how to deal with crackpot suggestions is central to learning critical thinking. Bad ideas teaches how good science should work.
If PF has a serious function, it should be not to close down uncomfortable discussions but instead to expose what faulty thinking looks like.
I have actually been to a lecture by Davis, by the way, and I find his ideas on evolution and cancer research to be really compelling. His suggestions about tracing this works similarly to his ideas of Mars, of going back to a time when it may have been habitable and how this could indeed initiate the biosignatures now on Earth. — TimeLine
Davies is one of my favourite scientists. He is more prepared than most to speculate wildly because that speculation could bring great rewards.
And unlike Crick, his speculation is careful. It always has a good metaphysical grounding.
It is also not without controversy. — TimeLine
How could any new and good idea be anything else than controversial? I don't get why you seem to think that a lack of controversy is a plus. If you aren't challenging accepted paradigms, then what is the point?
The trick is to be able to tell the difference between well-motivated challenges and charlatanism. But if you aren't living on the edge of controversy, you just ain't living.
Perhaps the prime moderating rule here should be "this isn't sufficiently controversial".
:)