Robert S. Siegler Robbie Case: A Modern Classic About 15 years ago, Robbie asked me what I thought of a talk we had just heard. I indicated that I hadn't much liked it and noted several serious problems. Robbie agreed with all of the criticisms, but said that he nonetheless liked the talk, because there was one good idea in it that he could use. I agreed with him that the idea was a good one, but it took me a while to understand the wisdom of his position. If there's one useful idea in a talk, then hearing it has been worthwhile, even if the talk also has numerous de?ciencies. On that day and on many others, talking with Robbie changed my thinking for the better. Robbie Case was in many ways a classic developmental psychologist of the old school. The depth and breadth of his theory; the range of age groups, populations, and topics that he studied; and his efforts to connect theory and application are all reminiscent of the greats of the past: Baldwin, Dewey, Piaget, Vygotsky, and Bruner.