One of the cases in which the development of such alleged reasons for behavior is best traced is that of the taboo. Although we ourselves have hardly any definite taboos, to an outsider our failure to use certain animals for food might easily appear from this point of view. Supposing an individual accustomed to eating dogs should inquire among us for the reason why we do not eat dogs, we could only reply that it is not customary; and he would be justified in saying that dogs are tabooed among us, just as much as we are justified in speaking of taboos among primitive people. If we were hard pressed for reasons, we should probably base our aversion to eating dogs or horses on the seeming impropriety of eating animals that live with us as our friends. On the other hand, we are not accustomed to eat caterpillars, and we should probably decline to eat them from feelings of disgust. Cannibalism is so much abhorred, that we find it difficult to convince ourselves that it belongs to the same class of aversions as those mentioned before. The fundamental concept of the sacredness of human life, and the fact that most animals will not eat others of the same species, set off cannibalism as a custom by itself, considered as one of the most horrible aberrations of human nature. In these three groups of aversions, disgust is probably the first feeling present in our minds, by which we re-act against the suggestion of partaking of these kinds of food. We account for our disgust by a variety of reasons, according to the groups of ideas with which the suggested act is associated in our minds. In the first case there is no special association, and we are satisfied with the simple statement of disgust. In the second case the most important reason seems to be an emotional one, although we may feel inclined, when questioned regarding the reasons of our dislike, to bring forward also habits of the animals in question that seem to justify our aversion. In the third case the immorality of cannibalism would stand forth as the one sufficient reason. Other examples are the numerous customs that had originally a religious or semi-religious aspect, and which are continued and explained by more or less certain utilitarian theories. Such are the whole group of customs relating to marriages in the incest group. While the extent of the incest group has undergone material changes, the abhorrence of marriages inside the existing group is the same as ever; but instead of religious laws, ethical considerations, often explained by utilitarian concepts, are given as the reason for our feelings. People affected with loathsome diseases were once shunned because they were believed to be stricken by God, while at present the same avoidance is due to the fear of contagion. The disuse into which profanity has fallen in English was first due to religious re-action, but has come to be simply a question of good manners.