Postulates of Probability


THE concept of probability has always comprised two ideas: that of frequency in an ensemble and that of reasonable expectation. Suppose it is said that in tossing an unbiased coin the probabilities of heads and tails are equal. It is implied that the fraction of tosses giving heads will be the same as the fraction giving tails in a large enough number of tosses. It is implied also that in a single trial there is as much reason to expect one result as the other. The choice of one or the other of these ideas as the primary meaning of probability distinguishes the two main schools of thought in the field.

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  1. 1

    Keynes, J. M., "A Treatise on Probability" (London, 1929).

  2. 2

    Jeffreys, H., "Theory of Probability" (Oxford, 1939).

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COX, R. Postulates of Probability. Nature 157, 517 (1946) doi:10.1038/157517a0

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