In physics, is it possible to trace the history of the idea that the known forces (electromagnetic, weak, strong and gravity) should be unified in a "Theory of Everything"? Would it go back to an influence from Parmenides' monism or is this too far-fetched?

Further, what has been the debate around this idea (if any) and what would be the different positions? This might veer into philosophy of physics, but has there been physicists opposed to seeking a ToE? (this would have to be recent history, since of course, a clear understanding that there are 4 forces probably dates back no farther than the middle of the 20th century).

  • $\begingroup$ I think this is way to broad and not really for this site, one can see it as a manifestation of the unity of science motif, but not very usefully. The first unification in the relevant enough sense was Maxwell's of electromagnetism with optics. Then their was Lorentz's ether-based unification of ponderable and imponderable matter, and it became a persistent archetype that deceptively seemed within reach at times. Einstein chased it all his life, and at one point Kaluza-Klein achieved it... right before the new interactions popped up. $\endgroup$
    – Conifold
    Apr 24, 2023 at 20:35
  • $\begingroup$ @Conifold Yes, I was afraid the question was too broad. Although you are esquissing a historical answer in your comment. Would it be more suitable for the philosophy StackExchange? Maybe phrased differently, as a question about justifications for physicists to look for unification or not? $\endgroup$
    – Frank
    Apr 24, 2023 at 20:37
  • $\begingroup$ It is not quite the right angle. With these aspirational proposals, justification is not really an issue. It is something one works toward and it works out or not. The proof is in the eating and there is no eating until it's cooked. If a positive solution becomes available it always defeats skeptics, so there is little point bothering with them either before or after. To get a hearing, one needs a viable alternative instead. See the philosophical parts of Cao-Schweber, pp. 69-90 for an empiricist one that envisions infinite regress of revisions. $\endgroup$
    – Conifold
    Apr 24, 2023 at 20:52
  • $\begingroup$ @Conifold How about a question on the philosophy stack exchange about the consequences of the success or failure of a unification program? $\endgroup$
    – Frank
    Apr 24, 2023 at 21:40
  • $\begingroup$ I am not sure how we would know that it failed. It is one of those perennial things: either it succeeds, or it didn't succeed yet. I guess the failure would mean that some alternative is the case. Maybe just stick to one side of it per question: metaphysical implications of ToE along the current lines; currently contemplated philosophical alternatives in case physics admits no ToE. $\endgroup$
    – Conifold
    Apr 24, 2023 at 23:18


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