...we have no right to decide off-hand that it is an unnatural pleasure to eat sawdust. A man might be constituted so that he liked it. And so long as his peculiarity doesn't damage or interfere with other people, there's no reason why he shouldn't be left alone. But if it is the man's fixed belief that sawdust eating is essential to human happiness; if he attributes almost everything that happens either to the effects of eating it or not eating it; if he imagines that most of the people he meets are also sawdust-eaters, and above all, if he thinks that the salvation of the world depends entirely upon making laws to compel people to eat sawdust, whether they like it or not, then it is fair to say that his mind is unbalanced on the subject; and that, further, the practice itself, however innocent it may appear, is in that particular case perverse. Sanity consists in the proper equilibrium of ideas in general. That is the only sense in which it is true that genius is connected with insanity.

Diary of a Drug Fiend