Nurture, when the Nurtures of the persons compared were not exceedingly different. I t appeared that when twins who had been closely alike had afterwards grown dissimilar, the date of divergence was usually referred to a time when one of them had a serious illness, sufficient to modify his constitution.
Many years later I was so harassed with the old question of Determinism, which would leave every human action under the control of Heredity and Environment, that I made a series of observations on the actions of my own mind in relation to Free Will. I employ the word not merely as meaning " unhindered " but in the special sense of an uncaused and creative action. I t was carried on almost continuously for six weeks, and off and on for many subsequent months . The procedure was this. Whenever I caught myself in an act of what seemed to be " Free Will " in the above sense, I checked myself and tried hard to recollect what had happened before, made rapid notes, and then wrote a full account of the case. To my surprise, I found, after some days' work, that the occasions were rare on which there seemed room for the exercise of Free Will as defined above. I subsequently reckoned that they did not occur oftener than once a day. Motives for all the other events could be traced backwards in succession, by orderly and continuous steps, until they led into a tangle of familiar paths. It was curious to watch the increase of power given by practice, of recalling mental actions which being usually overlooked give the false idea that much has been performed through a creative act, or by inspiration, which is really due to straightforward causation. The subject is too complex to be