Bergson regards knowledge of oneself as the optimal case of knowing; oneself, he thinks, is the sample of reality which best serves for an acquaintance with the nature of reality in general. “The existence of which we are most assured and which we know best is unquestionably our own, for of every other object we have notions which may be considered external and superficial, whereas, of ourselves, our perception is internal and profound.”[118] It is this perfect or optimal relation of identity or inwardness--which one bears to oneself--that is the condition of true (_i. e._ intuitive) knowledge. And in this case we find existence to be a perpetual flow of transition. That we think of our states as distinct from each other is due to the fact that reflection on one’s own existence is, unlike the flow of that existence itself, necessarily discontinuous. It is only now and then that motives arise which turn the attention to the self as an object, like others, for examination. The flow of change is not uniform, to be sure. It is quite imperceptible to our reflective attention most of the time, but if it ever ceased, we should at that moment cease to exist. Only the relatively sudden and interesting periods of transition get our attention. Then we see a new “state of consciousness” which we add to the others that we have mentally strung together in a temporal line. So we conceive of our history as the sum of elements as distinct as beads on a string. This intellectualistic view of the self eliminates the peculiar characteristic of its reality, namely, its duration, or the flow of its change, like a snowball, accumulating its substance as it rolls, duration goes on preserving itself in incessant change that accumulates all its past. Time, Bergson says, is the very stuff the psychological life is made of. “There is, moreover, no stuff more resistant nor more substantial.”[119]