W. V. O. Quine and then Jaakko Hintikka (the first needs no introduction, the second
to need none but, I think, because he wasn't so well-placed (wasn't Quine an actual member of the Vienna Circle?), he isn't so "prestigious" among non-specialists - although
The fourth video from the top is part 3 of a much longer series that you can view on Youtube. The last two videos were recently posted by guess who .
Hintikka speaks casually of "structures" and what he means by this (for the uninitiated) is explained in Laugwitz's intellectual biography of Riemann (I believe an English translation exists of this book). He also explains further in "The Emperor's New Intuitions" (1999) which is required reading not just for that reason.
An underrated figure is Richard R. M. Martin , an extreme nominalist (and opponent of Hintikka). Goodman is notable not just for the "grue" but his comments on " similarity " (that I might have more to say about later).