WHAT IS SO IMPORTANT ABOUT WHO DISCOVERED THE ELECTRON (OR ANYTHING ELSE)?

Was there a discoverer of the electron? Was it Thomson? Have I need­lessly complicated the issue with recondite distinctions that permit no definitive answers, as philosophers are wont to do? I think the issue is complicated, much more so than when I first began to think about it.

First, the philosophical account of discovery that I propose involves three factors: ontological (the thing discovered must exist); epistemic (the discoverer must be in a certain knowledge-state with respect to it); and priority (this state must be a first). Second, contrary to the opposing views mentioned, discovery does not require either manipulation and measure­ment of the item discovered or the idea of an important classification, or group recognition or consensus; nor is any of these sufficient. Further­more, one can be the discoverer of some entity even if one's beliefs about it are substantially false and even if many persons contributed to making that discovery possible.

Third, my account distinguishes a weak and a strong sense of discovery. In the weak but not the strong sense one can discover X even if the dis­coverer does not know it is X that has been discovered.

Fourth, in virtue of Thomson's magnetic deflection experiments, which were better than Perrin's, his electrostatic deflection experiments, which had not been achieved before, and his two independent determinations of m/e (better and more precise than the results produced by Wiechert), some case might be made that Thomson discovered the existence of charged particles that are electrons.

Now, why do, or should, we care about who discovered the electron, or any other entity? The question arises especially for my account of dis­covery. On that account, the fact that something has been discovered by someone does not by itself imply that what is discovered, or by whom, is important or interesting, even to the discoverer. (I may have discovered yet one more paperclip on the floor.) The importance of the discovery will depend on the item discovered and on the interests of the discoverer and of the group or individual to whom the discovery is communicated. Dis­covering a universal particle such as the electron, which is a constituent of all atoms, is obviously more important, especially to physicists, than discovering yet one more paperclip on the floor is to them or to me.

Not only can the object discovered be of importance, but so can the method(s) employed. In his discovery of the electron (at least for him­self) Thomson discovered a way to produce electrostatic deflection of the cathode rays, which had not been achieved before. Using this he devised a new independent way to obtain a fundamental measurement of mass- to-charge.

There is another point worth emphasizing about discoveries of certain entities, particularly those that are too small, or too far away, or otherwise too inaccessible to be observed directly. Scientists may have theoretical reasons for believing that such entities exist.

One reason may simply derive from a primal desire or curiosity to “see” or detect something by confronting it more or less directly. Another more important reason is to discover new facts about it, which is usually facilitated by observing it or its effects, and which may allow the theory that entailed its existence to be extended. It will also provide additional support for that theory without necessarily increasing the degree of prob­ability or confidence one attaches to that theory.^[253]

Why should we care about who, if anyone, was the discoverer, that is, about who was the first to be in an appropriate epistemic state for dis­covery with respect to some entity? It depends on who the “we” is and on what is discovered. As noted, not all discoveries and discoverers are of interest to all groups; some may be of interest to none. If what is dis­covered is important to some community, and if there was a discoverer, whether a person or a group, then simply giving credit where credit is due is what is appropriate and what may act as a spur to future investigations. In this regard discovery is no different from other achievements. If accom­plishing something (whether flying an airplane, or climbing Mt. Everest, or discovering the electron) is valuable to a certain community, and some person or group was the first to do it, or if several persons independently were the first, then such persons deserve to be credited and perhaps hon­ored and rewarded by the community, especially to the extent that the accomplishment is important and difficult.

Whether Thomson deserves the credit he received for being the (or a) discoverer of the electron is, of course, of interest to him and to other contemporaries such as Lenard, Zeeman, and Crookes, who thought they deserved more credit. It should also be of interest to subsequent physi­cists, historians of physics, and authors of textbooks who write about the discovery. The answer to the question of who discovered the electron, and hence who deserves the credit, is, I have been suggesting, not so simple. Part of that answer depends upon establishing who knew what, when, and how, which in the electron case is fairly complex. The other part depends on establishing some reasonably clear concept of discovery. In this chapter I have attempted to contribute to each task, particularly the latter.

Finally, credit is deserved not only for discovering the existence of an important entity, but for other accomplishments with respect to it as well. Even if Lenard has some claim to priority for the discovery that cathode ray constituents are smaller than atoms, and even if in 1897 Thomson's arguments that his corpuscles are constituents of all atoms are not con­clusive, we can admire and honor Thomson, among other reasons, for the experiments leading to the conclusions he drew, for the conclusions themselves, and for proposing and defending a bold idea that revolution­ized physics: that the atom is not atomic.

3. Or, in a tighter formulation, where the explanans is a set or conjunction of sentences:

(i) no subset of these all members of which are singular sentences entails the explanandum;

(ii) the explanandum is not entailed by a singular conjunct in a conjunctive equivalent of the explanans. To explicate the latter let S be a sentence containing within it one or more occur­rences of some singular sentence (or some compound of singular sentences) P. Delete from S one or more occurrences of P, obtaining a sentence S*. Form a conjunction of S* with P If this conjunction is equivalent to S it is a conjuctive equivalent of S containing P as a singular conjunct. For example, (a) “(Ga v Ja) & -Ja & (x) (Fx o Gx)” is a conjunctive equivalent of (b) “(x) ((Ga v Ja) & -Ja & (Fxo Gx)),” which contains “(Ga v Ja) & -Ja” as a singular conjunct.

2. Nagel’s analysis seems to come to this: The function of x in S is to y if and only if x is necessary (or sufficient or both)for S to do y and S is a goal-directed system with some goal G.

3. To say that this button activates the exploding mechanism is to imply, of course, that it is capable of doing this, and not that the mechanism is always being activated. In such a