A few days ago I mentioned the significance of reliable, local informants to those of us working on topics in another science. I just learned that Warren Samuels died. Samuels was one of the great, tireless historians and methodologists of the 20th century.
Warren was one of my earliest mentors in all matters pertaining to economics. (Thanks to the internet he started his mentoring before we met in person.) In fact, before I had completed my PhD (at Chicago) he called my attention to the existence of a related PhD (on Newton and Adam Smith) in economics (at Cambridge) by Leonidas Montes, who became a decisive interlocutor then. A few years later, Leon and I dedicated our first jointly edited volume, New Voices on Adam Smith, to "Warren Samuels whose invisible hand promotes the best kind of intellectual Exchange." Warren never tired of answering my naive questions.
Warren was the first person to ever acknowledge my research in public. My career was floundering and I thought that I would never find an audience among economists or philosophers. It was such a great morale boost! He also published my long study of the methodology of the Wealth of Nations, when others didn't want to touch it. Once, I saw him debate Nobel Laureate, James Buchanan, in person. Despite their fierce ideological differences, the two of them combined mutual respect, great knowledge of economics and (much to my surprise) deep philosophic learning.
UPDATE: Here's the obituary of Warren by Ross Emmett (one of my other mentors in the history of economics). I quote one passage: "His goal and passion was to broaden and enrich that conversation, and he was as happy to engage in conversation with a young scholar as he was with a Nobel laureate. To that end, he and Sylvia made a substantial contribution to the History of Economics Society to endow its Young Scholars program." (For striking evidence of the significance of this see here.) See also this moving tribute by Pete Boettke.