These names are given to errors caused by offending against the following rules:
Ignorance of these two rules leads to curious cases of self-deception. A person might argue, quite legitimately, that a certain proposal, if carried into effect, would result in this or that or the other advantage. Often before the end of the argument he will have persuaded himself that it would result in this and that and the other advantage. It is a common occurrence to find a person thinking that, if the chances of one event are, say, 6 in 10, and those of another event 7 in 10, the chances of both events coming off are about the same; whereas the mathematical chances of the double event are only 42 in 100, i.e., a little over 4 in 10.
"I can't go to Church every Sunday," is often put forward as an excuse for not going at all! "It is quite impossible for me to respond to all the charitable appeals that are made to me" is a convenient excuse for not responding to any.
I found the following extract in the 1935 Election Address of a Labour candidate:
"Modern technique is able to create continually greater wealth with the employment of fewer persons and, so far as the majority of them are concerned, less skilled persons. This means that a smaller proportion of the total wealth is distributed in wages and salaries, and that, as the bulk of our population maintains itself out of wage and salary earnings, the majority of the people receive a proportionately smaller share of the total social product."
This well illustrates the fallacy arising from neglect of the rules we have just been discussing. The first sentence applies to certain particular industries, and not to industry as a whole, in which the aggregate of employment tends to increase. The second sentence applies to "total wealth" the argument which has been made good only for particular industries, and it ignores (a) the vast increase in the total wealth of the country, (b) the increasing number of new industries. Did the writer really seriously contend that the share of the wage-earner, including State services (education, insurance, public health services, pensions, etc.), was less in 1935 than, say, in 1825?