We should get used to the idea that we’ll probably never be able to find – and confirm – a good explanation of the ultimate origin of the universe, though I see no reason to believe that we can’t press much further on this question than we have managed to date. In 50 years – or 20 years, or 200 years – our current epistemic horizon (the Big Bang, roughly) may look as parochial as the horizon Newton had to settle for in his day, but no doubt there will still be good questions whose answers elude us. And, of course, we never confirm any scientific answer in any absolute sense. As for questions science shouldn’t tackle, I think we should apply the rule that if nobody can think of any good that might come from knowing the answer, and there is clearly some harm that might come from knowing the answer, we should postpone research on that question indefinitely. Today most people at risk of Huntington’s chorea choose not to take the test that would tell them, with very high probability, whether they will succumb to the disease; the day a cure or treatment comes on line (and there is heartening progress on it, now that the critical proteins have been identified), those same people will want to take the test, because if the result is positive, there will be a course of action for them to take, and not just despair. No doubt advances in medical diagnosis and molecular biology will provide other such opportunities we may want to shelve for the time being.