Nicolas Poussin (1594-1665) was the greatest French artist of the 17th century, the founder of his country's classical school. With him, French painting shook off its provinciality and became a European affair, mirroring the power of its grand siecle, the age of Louis XIV. After Poussin, Rome could no longer condescend to Paris. But without Rome there would have been no Poussin: Rome formed and trained him, gave him his conception of professional life, his myths, his essential subjects, his sensuality and measure -- in short, his pictorial ethos.
He first went there in 1624 and stayed 16 years. What did...