バートランド・ラッセル 私の執筆法 n.2 在意識における孵化期間（松下彰良 訳) - Bertrand Russell : How I write, 1951.

Very gradually I have discovered ways of writing with a minimum of worry and anxiety. When I was young each fresh piece of serious work used to seem to me for a time-perhaps a long time-to be beyond my powers. I would fret myself into a nervous state from fear that it was never going to come right. I would make one unsatisfying attempt after another, and in the end have to discard them all. At last I found that such fumbling attempts were a waste of time. It appeared that after first contemplating a book on some subject, and after giving serious preliminary attention to it, I needed a period of sub-conscious incubation which could not be hurried and was if anything impeded by deliberate thinking. Sometimes I would find, after a time, that I had made a mistake, and that I could not write the book I had had in mind. But often I was more fortunate. Having, by a time of very intense concentration, planted the problem in my sub-consciousness, it would germinate underground until, suddenly, the solution emerged with blinding clarity, so that it only remained to write down what had appeared as if in a revelation.
The most curious example of this process, and the one which led me subsequently to rely upon it, occurred at the beginning of 1914. I had undertaken to give the Lowell Lectures at Boston, and had chosen as my subject "Our Knowledge of the External World". Throughout 1913 I thought about this topic. In term time in my rooms at Cambridge, in vacations in a quiet inn on the upper reaches of the Thames, I concentrated with such intensity that I sometimes forgot to breath and emerged panting as from a trance. But all to no avail. To every theory that I could think of I could perceive fatal objections. At last, in despair, I went off to Rome for Christmas, hoping that a holiday would revive my flagging energy. I got back to 'Cambridge on the last day of 1913, and although my difficulties were still completely unresolved I arranged, because the remaining time was short, to dictate as best as I could to a stenographer. Next morning, as she came in at the door, I suddenly saw exactly what I had to say, and proceeded to dictate the whole book without a moment's hesitation.