" Science _qua_ science? No. (It cannot reach the first conclusion, only the second.) Individual scientists? Yes, depending upon the situation, and always provisionally."
But if science cannot reach the "no possible natural mechanism" conclusion, then no scientist can, because it is not a valid scientific conclusion.
That does not mean that no scientist can privately believe that conclusion; it just means that no scientist can use it as a valid scientific conclusion. Newton, for example, had no scientific explanation for how gravity worked, and when confronted on this issue refused to speculate. That was his scientific position, which he never wavered from. But in his private writings he was convinced that what he called "gravity" was actually the miraculous action of angels pushing the planets to keep them moving and in orbit. If Newton had believed that this was a valid scientific explanation, he would have included it in his _magnum opus_, but he didn't, so he kept it to himself. Similarly a scientist might privately believe (because of theological or other non-scientific reasons) that the only way to explain a particular natural phenomenon is by invoking supernatural forces, but scientifically he would know that such a conclusion is invalid, so instead would opt for the "no known natural
mechanism" conclusion. Besides, that would be a good way for him to hedge his bets, because he should know that the historical precedence of science teaches that there is an excellent chance he will turn out to be wrong. Ultimately Newton was.
"As always, the community tends to focus its resources on problems it believes it can profitably pursue; however, that does not mean it should *completely* give up on an 'no known natural mechanisms' problem, no matter how intractible it seems at the moment."
You are arguing apples to my oranges again. Science would only completely give up on a "no possible natural mechanism" problem, because such problems (once recognized for what they are) are beyond the ability of science to investigate. However, science encounters "no known natural mechanism" problems all the time; the history of science is filled with them. Science never gives up on them, even if individual scientists do. There will always be new scientists ready to tackle the challenge, and eventually a natural mechanism will be discovered, though it might take a few generations to do so.
Kevin L. O'Brien