Did Einstein ever engage the "scientific method" of empirical investigation in the course of his work on special and general relativity; and if not, wasn't he more a philosopher of science (albeit an exceptionally productive and influential one) than a scientist? If Einstein simply engaged in a priori reasoning and conceptual analysis (using his famous thought-experiments) then I don't see why the physics community has any more claim to him than the philosophical community. After all, it seems that his methodolgy bore a much stronger resemblance to that of contemporary philosophical efforts than it does to anything going on in or commonly associated with physics departments. -Will Leonard

An excellent question!

Many of Einstein's most famous papers make shockingly few references to the details of previous empirical work by other scientists. To put the same point in another way, many of Einstein's most famous arguments arise largely from "philosophical" considerations. For instance, Einstein's 1905 special theory of relativity paper begins by noting a symmetry in electromagnetism: that the current induced by a magnet moving relative to a loop of conducting wire is the same, according to electromagnetic theory, whether the magnet is moving and the conductor is at rest, or vice versa, as long as their relative motion is the same in both cases. However, Maxwell's electromagnetic theory (as it was then understood) assigns the induced current different causes in the two cases. Einstein suggests that the current should be understood as having the same cause in the two cases, which leads him to suppose that there is no fact about whether a force is really electric or magnetic. Clearly, this argument invokes a kind of parsimony in explanation that has plenty of antecedents in philosophy. Furthermore, this argument is inspired by concerns about the reality of absolute motion, over and above relative motion, that go back at least to Newton and Leibniz.

Einstein was quite familiar with philosophical work on scientific reasoning -- such as Duhem's view that scientific theories are tested as a whole, rather than each bit of a scientific theory being tested individually and therefore having to make empirical predictions all by itself. Einstein also emphasized that in undermining the traditional picture of space and time, he was inspired by the thought that all scientific concepts are free creations in response to evidence rather than compulsory in virtue of the fixed structure of the human mind. In this regard, he cited Hume and Mach as important influences.

All of that being said, I would still want to insist that Einstein was a scientist doing science. His goal was to account for various observations, and his "thought experiments" were always in the service of that goal. For instance, Einstein said that he got heart palpitations when his calculations revealed that the general theory of relativity could account for the longstanding anomaly in the motion of Mercury. Of course, Einstein was a theorist, not an experimentalist. (There is the famous episode in which Hubble gave Einstein a tour of the gigantic California telescope at which Hubble discovered that the universe is expanding; during the tour, Mrs. Hubble allegedly said to Mrs. Einstein that this was the place where her husband discovered the structure of the universe, and Mrs. Einstein replied that her husband did that on the back of an envelope.) But Einstein's theories were aimed at addressing problems arising from science.

It is often difficult to say where philosophy ends and science begins. I would not want to insist on a sharp line demarcating them. (This point extends beyond physics. Do investigations into the evolutionary origins of moral and aesthetic sentiments constitute philosophy or science?) And I would not be eager to embrace the questioner's presupposition that there is a distinctive "scientific method." But I do regard Einstein as a scientist -- one whose work continues to have great philosophical significance and shows great philosophical sensitivity and courage.

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