The principles of science : $b a treatise on logic and scientific methodJevons, William Stanley
Philosophy
The principles of science : $b a treatise on logic and scientific method
Jevons, William Stanley
Logic; Science -- Methodology
Many persons have a fallacious tendency to believe that when a chance
event has happened several times together in an unusual conjunction, it
is less likely to happen again. D’Alembert seriously held that if head
was thrown three times running with a coin, tail would more probably
appear at the next trial.[125] Bequelin adopted the same opinion, and
yet there is no reason for it whatever. If the event be really casual,
what has gone before cannot in the slightest degree influence it. As
a matter of fact, the more often a casual event takes place the more
likely it is to happen again; because there is some slight empirical
evidence of a tendency. The source of the fallacy is to be found
entirely in the feelings of surprise with which we witness an event
happening by chance, in a manner which seems to proceed from design.
[125] Montucla, *Histoire*, vol. iii. p. 405; Todhunter, p. 263.
Misapprehension may also arise from overlooking the difference between
permutations and combinations. To throw ten heads in succession with a
coin is no more unlikely than to throw any other particular succession
of heads and tails, but it is much less likely than five heads and five
tails without regard to their order, because there are no less than
252 different particular throws which will give this result, when we
abstract the difference of order.
Difficulties arise in the application of the theory from our habitual
disregard of slight probabilities. We are obliged practically to accept
truths as certain which are nearly so, because it ceases to be worth
while to calculate the difference. No punishment could be inflicted
if absolutely certain evidence of guilt were required, and as Locke
remarks, “He that will not stir till he infallibly knows the business
he goes about will succeed, will have but little else to do but to
sit still and perish.”[126] There is not a moment of our lives when
we do not lie under a slight danger of death, or some most terrible
fate. There is not a single action of eating, drinking, sitting down,
or standing up, which has not proved fatal to some person. Several
philosophers have tried to assign the limit of the probabilities
which we regard as zero; Buffon named 1/10,000, because it is the
probability, practically disregarded, that a man of 56 years of age
will die the next day. Pascal remarked that a man would be esteemed a
fool for hesitating to accept death when three dice gave sixes twenty
times running, if his reward in case of a different result was to be a
crown; but as the chance of death in question is only 1 ÷ 6^{60}, or
unity divided by a number of 47 places of figures, we may be said to
incur greater risks every day for less motives. There is far greater
risk of death, for instance, in a game of cricket or a visit to the
rink.
[126] *Essay concerning Human Understanding*, bk. iv. ch. 14. § 1.
Public-domain text, read in full here on John Shaqi.
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