Hostname: page-component-848d4c4894-x24gv Total loading time: 0 Render date: 2024-05-27T21:51:11.327Z Has data issue: false hasContentIssue false

Bertrand's Paradox and the Principle of Indifference

Published online by Cambridge University Press:  01 January 2022

Abstract

The principle of indifference is supposed to suffice for the rational assignation of probabilities to possibilities. Bertrand advances a probability problem, now known as his paradox, to which the principle is supposed to apply; yet, just because the problem is ill-posed in a technical sense, applying it leads to a contradiction. Examining an ambiguity in the notion of an ill-posed problem shows that there are precisely two strategies for resolving the paradox: the distinction strategy and the well-posing strategy. The main contenders for resolving the paradox, Marinoff and Jaynes, offer solutions which exemplify these two strategies. I show that Marinoff's attempt at the distinction strategy fails, and I offer a general refutation of this strategy. The situation for the well-posing strategy is more complex. Careful formulation of the paradox within measure theory shows that one of Bertrand's original three options can be ruled out but also shows that piecemeal attempts at the well-posing strategy will not succeed. What is required is an appeal to general principle. I show that Jaynes's use of such a principle, the symmetry requirement, fails to resolve the paradox; that a notion of metaindifference also fails; and that, while the well-posing strategy may not be conclusively refutable, there is no reason to think that it can succeed. So the current situation is this. The failure of Marinoff's and Jaynes's solutions means that the paradox remains unresolved, and of the only two strategies for resolution, one is refuted and we have no reason to think the other will succeed. Consequently, Bertrand's paradox continues to stand in refutation of the principle of indifference.

Type
Research Article
Copyright
Copyright © The Philosophy of Science Association

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

I have to thank two anonymous referees and Michael Dickson for comments, Michael Clark for discussion, and Man-shun Yim of Hong Kong, whose note to Clark about the nonexistence of a bijection from chords to their midpoints drew me into thinking further about the paradox.

References

Andersen, Kirsti (1985), “Cavalieri’s Method of Indivisibles,” Archive for History of Exact Sciences 31:291367.Google Scholar
Bertrand, Joseph Louis François (1888), Calcul des probabilités. Paris: Gauthier-Villars.Google Scholar
Capinski, Marek, and Kopp, Peter Ekkehard (1999), Measure, Integral, and Probability. London: Springer.CrossRefGoogle Scholar
Clark, Michael (2002), Paradoxes from A to Z. London: Routledge.CrossRefGoogle Scholar
De Finetti, Bruno (1970), Theory of Probability. Vol. 1. New York: Wiley.Google Scholar
Edwards, Robert E. (1995), Functional Analysis. New York: Dover.Google Scholar
Jaynes, Edwin T. (1973), “The Well Posed Problem,” Foundations of Physics 4 (3): 477492..CrossRefGoogle Scholar
Keynes, John Maynard ([1921] 1963), A Treatise on Probability. London: Macmillan.Google Scholar
Kolmogorov, Andrei Nikolaevich (1956), Foundations of the Theory of Probability. 2nd English ed. New York: Chelsea.Google Scholar
Marinoff, Louis (1994), “A Resolution of Bertrand’s Paradox,” Philosophy of Science 61 (1): 124..CrossRefGoogle Scholar
Van Fraassen, Bas C. (1989), Laws and Symmetry. Oxford: Clarendon.CrossRefGoogle Scholar
Weir, Alan (1973), Lebesgue Integration and Measure. Cambridge: Cambridge University Press.CrossRefGoogle Scholar
Williamson, Jon (1999), “Countable Additivity and Subjective Probability,” British Journal for the Philosophy of Science 50 (3): 401416..CrossRefGoogle Scholar