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nydus/The Logic of Chance, 3rd EditionPublic
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THE SUBJECTIVE SIDE OF PROBABILITY. MEASUREMENT OF BELIEF.

4 It is necessary to take an example in which the man is forced to act, or we should not be able to shew that he has any belief on the subject at all. He may declare that he neither knows nor cares anything about the matter, and that therefore there is nothing of the nature of belief to be extracted out of his mental condition. He very likely would take this ground if we asked him, as De Morgan does, with a slightly different reference (Formal Logic, p. 183), whether he considers that there are volcanoes on the unseen side of the moon larger than those on the side turned towards us; or, with Jevons (Principles of Science, Ed. II. p. 212) whether he considers that a Platythliptic Coefficient is positive. These do not therefore seem good instances to illustrate the position that we always entertain a certain degree of belief on every question which can be stated, and that utter inability to give a reason in favour of either alternative corresponds to half belief.

5 Except indeed on the principles indicated further on in §§ 24, 25.

6 For a fuller discussion of this, see the Chapter on Causation.

7 The best example I can recall of the distinction between judging from the subjective and the objective side, in such cases as these, occurred once in a railway train. I met a timid old lady who was in much fear of accidents. I endeavoured to soothe her on the usual statistical ground of the extreme rarity of such events. She listened patiently, and then replied, “Yes, Sir, that is all very well; but I don't see how the real danger will be a bit the less because I don't believe in it.”

8 This would still hold of empirical laws which may be capable of being broken: we now have very much shifted the word, to denote an ultimate law which it is supposed cannot be broken.

CHAPTER VII.

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