The more certain existence and the better we know is indisputably ours, because, of all other objects, we possess external and superficial triable notions, while we perceive ourselves internally, deeply. What do we check then? What is, in this exceptional case, the meaning of the verb 'to exist'?
First I see that I passage from one state to another state. I'm cold or heat, I'm happy or sad, I work or do nothing, I look around me or think about something else. Sensations, feelings, volitions, representations, such are the modifications among which distributes my existence and which color it alternately. I change, then, without ceasing. (p.13)
Thus the anthology of Henri Bergson (1957), conducted by Gilles Deleuze, starts, with this text of L'évolution creatrice, direct and full of content. And follows:
(...) I say, and rightly so, that I change, but the change seems to reside in the passage from one state to the next state: for each state, considered separately, I believe that is still what it was all the time that it occurred. However, a slight effort of attention would reveal me that there is no affection, representation or volition which is not modified at all times; if a state of the soul cease to vary, its duration would cease to pass.
(...) But it is comfortable not pay attention to this continuous change, and noticing only when it grows enough to print a new attitude to the body, and a new direction to attention. Just then, we find that we have changed state. The truth is that we are constantly changing, and that the state itself is already change.
(...) Because we close our eyes to the unceasing variation of every psychological state, we are obliged, when the variation has become so significant that requires our attention, talking as if a new state had been juxtaposed to precedent. Of that we assume that, in turn, is unchanged, and thus consecutively and indefinitely. The apparent stability of psychological life resides, therefore, that our attention is fixed on it through a series of discrete acts; where no more than a smooth slope, following the broken line of our acts of attention, we perceive the rungs of a ladder. True that our psychological life is full of unexpected events. Thousand incidents that seem cut with what precedes them but without being linked to what follows them arise. But the discontinuity of their appearances highlights on the continuity of a background on which they are drawn and they are due to the same intervals that separate them: they are the timbal beats exploding from time to time in the symphony. Our attention fixes on them because it is more interested on them, but each is carried by the fluid mass of our entire psychological existence. Each of them is simply the best illuminated point of an unstable area that includes everything we feel, think, want, all that ultimately we are at a given time. It is this whole area which is actually our state. Now, on states thus defined can be said to be no different elements. They are continued to each other in an endless course. (p.13-15)
We perceive our existence as a sequence of jumps in time from a psychological state to another. Each state is the 'best illuminated point' of all our possible thoughts, feelings and desires at every given moment. And the adequacy or appropriateness regarding the stimulus or situation is the one that makes light the spark that illuminates a specific 'point' and not another. So, what is in our consciousness is, of all that has our mind, which best is linked to the situation to which we are exposed, assuming that the situations we encounter very often are completely unpredictable to our own mind, do not depend on us.
What we will find out there there is no way to know, but we try throught our beliefs, assumptions, prejudices, etc. which are a way to be expectant, but, in retrospect, we see that rarely achieve their goal of foreseeing the future . So, if we can not foresee what just strictly is going on, does it make sense to ask ourselves what will happen? We can not stop doing, we always do, in fact. We can not predict the future but to prepare how we respond and how we perceive, if not all possible situations, at least those situations we know that are most likely, even knowing that the future will end up surprising us. We must be constantly alert and expectant with no remedy.
Going deep in the question, can we know if the situations of the environment will be distributed in a uniform way or not over time? This is, can we know when something unpredictable will happen? Clearly, no. With regard to the sensory external world we can not say that evolves in a uniform way, nor otherwise.
Regarding the inner world of sensations that originate in the functioning of our body, we can only say that they follow the proper laws and times of biology. The different life processes also evolve very differently. In any case, what we know about them is that time on them is not uniform but quite the opposite: they progress with great variability, as impulses, pulses, cycles, phases...
So, to know ourselves, the succession of our psychological states, the phenomenology of our existence, urges us to know how our body works, its biology, but no longer in itself, but in terms of sensory and conscious phenomena it produces.
Bergson, H. (1957). Memoria y vida. Madrid: Alianza