Thursday, August 18, 2011

Against rationalism

Cosmologist Sean M. Carroll writes on his Cosmic Variance blog:
Believing that something must be true about the world because you can’t imagine otherwise is, five hundred years into the Age of Science, not a recommended strategy for acquiring reliable knowledge. It goes back to the classic conflict of rationalism vs. empiricism. “Rationalism” sounds good — who doesn’t want to be rational? But the idea behind it is that we can reach true conclusions about the world by reason alone. We don’t ever have to leave the comfort of our living room; we can just sit around, sharing some single-malt Scotch and fine cigars, thinking really hard about the universe, and thereby achieve some real understanding.
You would think that the necessity for science to rely on empirical investigation would have been settled centuries ago, but there is a widespread and pernicious academic belief that Copernicus and Einstein proved the superiority of rationalism. As commenter and mathematician Samuel Prime says:
Didn’t Einstein arrive at his two theories of relativity by an approach similar to rationalism? He hardly had much experimental basis for making the postulates he made in these theories. (The tests came some years later.) I think beauty and simplicity were among the driving forces in his rationalism.
No, this is a big myth, as rebutted in my comments at the above blog, and in my book.

Samuel's strongest argument for Einstein's priority is that Lorentz credited Einstein:
Further, Lorentz made the following comment regarding Einstein’s relativity:

“I considered my time transformation only as a heuristic working hypothesis. So the theory of relativity is really solely Einstein’s work. And there can be no doubt that he would have conceived it even if the work of all his predecessors in the theory of this field had not been done at all. His work is in this respect independent of the previous theories.”

Lorentz, H.A. (1928), “Conference on the Michelson-Morley Experiment”, The Astrophysical Journal 68: 345-351
This is really some strained praise for the man who was, by then, the most famous scientist in the world. All new physical theories are heuristic working hypotheses. All work is original if you assume that the author would have reinvented all the work of his predessors.

Lorentz generously credited Einstein. It is true that Einstein's papers included explanations of some points omitted by Lorentz. Einstein's work can be considered independent of previous theories if you assume that Einstein would have conceived the work of all his predecessors. That is right. But it does not change the facts that those theories were conceived before Einstein, that Einstein only postulated what his predecessors proved, that this was the opinion of Lorentz, Einstein, Minkowski, and everyone else at the time, and that Lorentz credited Poincare over Einstein.

1 comment:

  1. Great stuff. It is clearly not possible to consider thought experiments as purely 'a priori' process. I can quote Einstein's criticism:
    "For one will always be able to say that critical philosophers have until now erred in the establishment of the a priori elements, and one will always be able to establish a system of a priori elements that does not contradict a given physical system. Let me briefly indicate why I do not find this standpoint natural. A physical theory consists of the parts (elements) A, B, C, D, that together constitute a logical whole which correctly connects the pertinent experiments (sense experiences). Then it tends to be the case that the aggregate of fewer than all four elements, e.g., A, B, D, without C, no longer says anything about these experiences, and just as well A, B, C without D. One is then free to regard the aggregate of three of these elements, e.g., A, B, C as a priori, and only D as empirically conditioned. But what remains unsatisfactory in this is always the arbitrariness in the choice of those elements that one designates as a priori, entirely apart from the fact that the theory could one day be replaced by another that replaces certain of these elements (or all four) by others. (Einstein 1924, 1688–1689)"

    Einstein's point is that while one can always choose to designate selected elements as a priori and, hence, non-empirical, no principle determines which elements can be so designated, and our ability thus to designate them derives from the fact that it is only the totality of the elements that possesses empirical content. Relativity theory is conceptually brilliant, yet visually basic enough, that most teenagers can imagine. While a priority may be the medium of thought experiments, it cannot account for the selection and arrangement of elements , into a coherent whole.