Just learned of his passing via Mankiw (via Eli Dourado’s twitter feed). He’s most closely associated with “economic imperialism”, which might be summed up as applying economics to subject matter normally investigated by sociology. Plenty of pop “economics of everyday life” has followed afterward, with his clearest acolyte being Steven “Freakonomics” Levitt. I cited (or re-cited, since Albert O. Hirschman’s citation is what alerted me) a classic Becker paper on the economics of irrational agents here.