I think it's obviously true that some explanations are more fundamental than others. We have, e.g. a more fundamental explanation of tides than anyone did in 500AD. That is not to deny that it is difficult to make precise what exactly it is that makes one explanation more 'fundamental' than another. As always, individual cases are clear; the general principle is elusive.
>He's alluding to the idea that that question isn't well defined.
It's well-defined enough to answer. Hundreds of millions of school children learn a perfectly sensible answer to the question every year. (Would this answer satisfy someone with a PhD in physics? Obviously not. But that's not the point.)
It's in any case bizarre to insist that a layperson ask a question that's well-defined according to the standards of a particular field.
>He's alluding to the idea that that question isn't well defined.
It's well-defined enough to answer. Hundreds of millions of school children learn a perfectly sensible answer to the question every year. (Would this answer satisfy someone with a PhD in physics? Obviously not. But that's not the point.)
It's in any case bizarre to insist that a layperson ask a question that's well-defined according to the standards of a particular field.