Scholars put the question expressed by the title of this roundtable discussion [What do history and philosophy of science have to offer one another?] with some urgency nowadays. It is often as if the questioner thinks that the very continuation of the two specializations depended upon an answer to the question now. Things do not seem to me to require the sense of urgency, any more than they are made better by one of two relatively — complacent attitudes: "Well, the importance of history to philosophers of science has now been demonstrated, let us turn to questions of what, if anything, philosophy has to offer the historian of science"; or, "Well, we know that all history of science is infested with philosophical considerations, let us turn to the question of whether or not historians have anything relevant to say to philosophers of science." I think it is not often enough appreciated that both history and philosophy of science, as special research and teaching disciplines, are relatively new. After all, it is only in our Century that history of science has become a fully mature and self-conscious technical discipline just as it is only in our Century that philosophy of science, armed with more powerful technology in the form of logic and techniques of analysis, has become, rightly or wrongly, a separable aspect of philosophy.