A more important result of the inquiry is to lead us on to an application of the method of difference.  Starting with this strong probability that the improvement is due to the new form of government, we can go a step further and examine a single case, in order to establish more clearly the sequence of events which we call a cause.  In the case of any given town which has adopted the commission government the material for the application of the method of difference is ready to our hands, if nothing else has been changed in the town but the form of government.  The inhabitants and the voters are the same, the physical conditions are the same.  If now we seek for the cause of an admitted improvement in the administration of the city affairs, we are driven to ascribe it to the only factor in the case which has been changed, and this is the form of government.  Such an argument, if supported by figures and specific facts, is obviously strong.

The same kind of argument is constantly used in the discussion of prohibition and local option as a means of reducing the amount of liquor consumed in a community, for the frequent changes both in states and in smaller communities provide material for the application of the same method of difference.  Here, however, the factors are more complex, on account of differences in the character of the population in different places, and their inherited habits as concerns the use of wine, beer, and other liquors.

40.  Faulty Generalization.  Both generalization through the method of agreement, and the assignment of causes through the method of difference, however, have their dangers, like all forms of reasoning.  A discussion of these dangers will throw light on the processes themselves.

The chief danger when you reason through the method of agreement is of jumping to a conclusion too soon, and before you have collected enough cases for a safe conclusion.  This is to commit the fallacy known as hasty generalization.  It is the error committed by the dogmatic sort of globetrotter, who after six weeks spent in Swiss-managed hotels in Italy will supply you with a full set of opinions on the government, morals, and customs of the country.  In a less crass form it affects the judgment of most Englishmen who write books about this country, for they come over with letters of introduction to New York, Boston, Chicago, and San Francisco, and then generalize about the rest of the country and its population.

We are all in danger from the fallacy, however, for it is a necessary law of the mind that we shall begin to make opinions and judgments on a subject as soon as we become acquainted with it.  The only safeguards are, in the first place, to keep these preliminary judgments tentative and fluid, and in the second, to keep them to one’s self until there is some need of expressing them.  The path to wisdom in action is through open-mindedness and caution.