It is with considerable diffidence that I bring this subject before such an Association as this. I should have the same feeling were I to argue before the Mathematical Society for the merits of the Multiplication Table, or before the Astronomical Society in favour of the Law of Gravitation. It is a matter that I have regarded as an axiom for the last five and twenty years, and that I fondly thought was established as a fundamental doctrine of alienism. My astonishment was great therefore, when, at a recent meeting of the Education Committee of this Association, my proposal, that the doctrine should find expression in the syllabus of subjects for the diploma in Psychiatry did not find a single supporter. The experience carried me back to the early years of my membership of this Association, when I constantly found myself in a minority of one in advocating views which are now become commonplaces. It seems, therefore, necessary to bring the matter formally before you, and to argue it out; and here I am in the difficulty felt by everyone who tries to prove formally what seems to him self-evident. I believe that things that are equal to the same thing are equal to one another. I do not know whether any of the members present share this belief. If they believe that conduct is of no importance in insanity, the same cast of mind may very well cause them to believe that things that are equal to the same thing are greater than one another, or that two straight lines can enclose a space, or that things that are unsupported fly upwards. But if they do believe that things that are equal to the same thing are equal to one another, they would have considerable difficulty in giving a reason for the faith that is in them. If I question the truth of it, and ask what are the grounds of their belief, I think I should place them in a quandary. I am in a similar quandary in demonstrating that disorder of Conduct is the prime element in Insanity.