(5) _Generalisation_ is only an instinctive process of simplification. As soon as we perceive a certain characteristic in an object, we extend this characteristic to all other objects which at all resemble it. In all human concerns, where the facts are always complex, we make generalisations unconsciously; we attribute to a whole people the habits of a few individuals, or those of the first group forming part of the people which comes within our knowledge; we extend to a whole period habits which are ascertained to have existed at a given moment. This is the most active of all the causes of historical error, and one whose influence is felt in every department, in the study of usages and of institutions, even in the appreciation of the morality of a people.[206] Generalisation rests on a vague idea that all facts which are contiguous to each other, or which resemble each other in some point, are similar at all points. It is an unconscious and ill-performed process of sampling. It may therefore be made correct by being subjected to the conditions of a well-performed process of sampling. We must examine the cases on which we propose to found a generalisation and ask ourselves. What right have we to generalise? That is, what reason have we for assuming that the characteristic discovered in these cases will occur in the remaining thousands of cases? that the cases chosen resemble the average? The only valid reason would be that these cases are representative of the whole. We are thus brought back to the process of methodical sampling.