The inner sense that each of us has of his own existence, and of what he experiences within himself, is the first source and principle of all truth of which we are susceptible. There is nothing more immediate to convince us that the object of our thoughts is as real as the thought itself, because this object and our thought, and the inner sense we have of them, are really nothing but we who think, who exist, who feel, and who have that feeling . Anything we could say to prove or further clarify this point would only obscure it; similarly, if we wanted to find something clearer than light, and go beyond it, we would find only shadows.

One must abide by this primary rule, which is as clear as the light of day, and which for this reason is called evidence of the highest order. Skeptics may well object that they doubt their existence; it would be a waste of time to amuse ourselves with showing them their foolishness and telling them that if they doubt everything, it is therefore true that they exist, for we cannot doubt without existing. It will always be within their power to retreat into ridiculous verbiage, where it would be equally ridiculous for us to try to win them over by force.

Although in our day no one falls into a skepticism so universal and thus so extravagant, since it goes so far as to extinguish all the lights of reason and to deny the existence of the inner sense that penetrates us, we can say nevertheless that we have never been closer to their opinion. Certain philosophers of our time have only exempted from this universal doubt into which they have plunged all their knowledge, this first rule or source of truth drawn from our inner sense ; they have deigned neither to recognize nor admit any other kinds of truth or evidence. Therefore when we ask them if it is evidentially certain that there are bodies, and that we receive impressions of them, they firmly answer no, and that we have no evident certainty regarding the matter, for we have not drawn this knowledge from the inner sense of our own experience, nor have we drawn it from one of its necessary consequences. That is what an English philosopher had absolutely no trouble publishing. [1]

Furthermore, it would be impossible to imagine what other evident certainties these philosophers would accept. The testimony of the senses, perhaps, divine revelation, human authority? Is it perhaps God’s immediate impression on us? The testimony of the senses being corporeal, it cannot be accepted by those who have not previously acknowledged the existence of the body. Divine revelation and human authority make an impression on us only through the testimony of the senses; in other words either through our eyes which have witnessed the miracles of the almighty, or through our ears which have heard the discourse of men who speak to us on behalf of God. Finally, the immediate impression of God implies the existence of a God, and a being different from me. But if the inner sense of what I experience is the only thing that is evident, then everything that is not formally this inner sense will not be evident to me at all.

From this principle, that the inner sense is the single rule of truth, follows first that we have no obvious certainty of the existence of bodies, not even of our own; for in the end, a spirit, a soul like ours, does clearly feel the impression bodies make on it, especially its own; but because in reality the body is very distinct from this impression, and since this impression could absolutely be experienced in our soul without the presence of bodies, it logically follows that our inner sense does not convince us of the existence of any bodies.

Second, another equally natural consequence is that we have no obvious certainty of what did or did not happen to us yesterday, not even whether or not we existed. For according to this absurd system, evidence is only available to me through inner perception which is always in the present. Now, at this moment I clearly perceive the memory of what happened to me yesterday; but this memory is but an inner perception of what I am currently thinking, in other words, a present thought, not identical to what happened yesterday, which no longer exists. For the same reason, I would be even less certain that I had not been in this world for two or three thousand years. Who will stop me from pushing this reasoning all the way to eternity, since we may very well always have existed, without remembering? If someone were to propose that we have been created, we could answer that we have no obvious certainty of that. For having been created is in the past, and is not either the present perception or the inner sense within us right now. I only have the present perception of the idea, by which I believe that I have existed before the moment in which I find myself presently.

Third and finally, another consequence as legitimate as the previous ones is that we have no certainty that there exist in the world any beings other than each one of us. We do have an inner perception of the impressions we receive, which we attribute to spirits and intelligences that supposedly live outside us; but this inner perception carrying no conviction except of itself, and being entirely internal, it offers no clear certainty of the existence of a being outside of us. In fact, according to this fine philosophy, the soul is not obviously certain if it is not naturally such that it experiences by itself and its constitution alone, the impressions whose causes it attributes to beings outside itself. It has thus no clear certainty that there exists any spirit beyond itself, or any being whatsoever; it therefore has no evidence that it has not existed forever, or even that it is not the only being in the world. Following a consequence this strange, it is not worth the trouble to indicate all the others that would come crowding in afterwards: to show that I have no evidence at all of whether I am currently awake or asleep; if I have the freedom to act or not to act, to will or not to will, etc. All these consequences leap out at us by themselves, without any necessity of noting them at length.

Since the consequences which logically follow this principle — that is, that the inner sense of our own perception is the only measure of truth — are so strange, so ridiculous, and so absurd, it is itself necessarily strange, ridiculous, and absurd, since it has been demonstrated that the consequences and the principle are the same thing. See Evidence and Common Sense.

Note

1. The reference is to the idealist philosopher George Berkeley (1685-1753). See the entry on him in the Stanford Encyclopedia of Philosophy.