Full Idea
Since 1750 empiricism shows five turns for the better. First was a shift from ideas to words. Second a shift from terms to sentences. Third the shift to systems of sentences. Fourth the abandonment of analytic-synthetic dualism. Fifth was naturalism.
Gist of Idea
Empiricism improvements: words for ideas, then sentences, then systems, then no analytic, then naturalism
Source
Willard Quine (Five Milestones of Empiricism [1975], p.67)
Book Reference
Quine,Willard: 'Theories and Things' [Harvard 1981], p.67
A Reaction
[compressed] Quine must be largely credited with the last two. The first four are almost entirely linguistic in character, which is characteristic of mid-twentieth-century empiricism. I would offer the recognition of explanation as central for the sixth.