We often assume that we shall retain a thing in our memory; and so thinking, we do not write it down. But afterwards, when we wish to recall it, it refuses to come to mind; and we are then sorry that we thought it would return to memory, or that we did not secure it in writing so as to prevent its escape; and lo, on a sudden, without our seeking it, it occurs to us. Then does it follow that we were not ourselves when we thought this? And that we cease to be the same thing that we were, when we are no longer able to think it? Now how does it happen that I know not how we are abstracted from, and denied to, ourselves; and similarly am ignorant how we are restored and returned to ourselves? As if we are other persons, and elsewhere, when we seek, but fail to find, what we deposited in our memory; and are ourselves incapable of returning to ourselves, as if we were situated somewhere else; but afterwards return again, on finding ourselves out. For where do we make our quest, except in our own selves? And what is it we search for, except our own selves? As if we were not actually at home in our persons, but had gone somewhither. Do you not observe, even with alarm, so deep a mystery? And what is all this but our own nature -- not what it has been, but such as it now is? And observe how much more we seek than we comprehend. I have often believed that I could understand a question which had been submitted to me, if I were to bestow thought upon it. Well, I have bestowed the thought, but have not been able to solve the question; and many a time I have not so believed, and yet have been able to determine the point. The powers, then, of my own understanding have not been really known to me; nor, I apprehend, have they been to you either.