This seemed to me to be an admirable excuse for my refusal, but served merely to increase their enthusiasm. They urged that previous writers on the subject had expressed different and at times contradictory opinions, between which it was very difficult to choose. They thought therefore that they were justified in imposing on me the task, if not of discovering original views, at least of passing definite judgment on those expressed by my predecessors.

I was moved to comply not so much because I felt confidence that I was equal to the task, as because I had a certain compunction about refusing. The subject proved more extensive than I had first imagined; but finally I volunteered to shoulder a task which was on a far larger scale than that which I was originally asked to undertake. I wished on the one hand to oblige my very good friends beyond their requests, and on the other to avoid the beaten track and the necessity of treading where others had gone before.