THE UNIVERSITY OF BRITISH COLUMBIA
Philosophy 1101 – Introduction to Philosophy
Logic, Rationality and Truth
In this week’s reading from the textbook, we read W. K. Clifford’s view that beliefs must
be supported by evidence.
But if the belief has been accepted on insufficient evidence, the pleasure is a
Not only does it deceive us by giving us a sense of power which
we do not really possess, but it is sinful, because it is stolen in defiance of our
duty to mankind.
The duty is to guard ourselves from such beliefs as from a
pestilence … (in
In the language used by logicians, we say that conclusions must be supported by premises.
Philosophers (in the analytic tradition), like W. K. Clifford, place a very high value on
logical arguments as a means to discover truth.
Consider, for example, the claim that s sometimes made, that “Heterosexual men are
more promiscuous than heterosexual women.”
According to do one survey, for example,
Men average 7 sexual partners per lifetime, and women only 4.
The claim above has been questioned on purely logical grounds, using the following
argument that attempts to establish a contrary conclusion.
The number of (heterosexual) men equals the number of
(heterosexual) women (at least approximately).
The average number of sexual relationships for men in the population is by
is the sum of all the numbers of such
relationships for individual men, and
the number of men.
It is clear
also equals the number of distinct (hetero)sexual
in the population, for each sexual partner that each man has defines a unique
sexual relationship, consisting of one man and one woman.
Further, the total
number of (hetero)sexual relationships involving females also takes this value
Then, since the number of women is also
, the average number of sexual
partners per woman is
(Heterosexual) Women are, on average, exactly as promiscuous
as heterosexual men.