of all sensations was, philosophically speaking, founded upon that of some one sensation. Every sensation is a contingent, individual fact: how then are we to draw from it light to guide us to necessary truths? No matter under what aspect we consider sensation, it is only an impression received through our organs. We are sure of the impression because it is intimately present to our mind; and its repetition aided by other sensations, whether of the same or another sense, makes us certain of its relations with the object producing it: but every thing is done instinctively, with little or no reflection; and we are always condemned, however much we reflect, to reach a point beyond which we cannot pass, for nature herself there stops us.
61. Far then from finding in any sensation a fundamental fact on which to found a philosophical certainty, we discover a collection of particular and mutually distinct facts, equal, however, so far as the production in us of that security which we call certainty is concerned. It is of no use to decompose man, and reduce him first to an inanimate machine, then allow him one sense, making him perceive different sensations, afterwards grant him another sense, making him combine the new and the old sensations, and so on synthetically to the possession and exercise of them all. These things may do to entertain one's curiosity, to nourish philosophical pretensions, or to give a show of probability to imaginary systems; but they are in reality of little or no use; the evolutions which the observer imagines do not resemble those of nature; and the true philosopher ought to examine what really is, not what is only in his conception.
Condillac, animating his statue by degrees, and making the whole sum of human knowledge flow from one sensation, is like those priests who got inside the statue of the idol, and thence emitted their oracles. It is not the statue which receives animation, that speaks and thinks, it is Condillac from within it. Let us, however, grant to the sensist all he demands; let us allow him to regulate as he pleases the mutual dependence of sensations; for the instant we require him to make use only of pure sensations in his discussions, he will be utterly disconcerted, how much soever he may suppose them to be transformed. But we reserve these questions to the place in which we shall examine the nature and origin of ideas.
62. Why are we sure that the agreeable sensation which we experience in our sense of smell proceeds from an object called a rose? Because we recollect having experienced the same sensation on a thousand other occasions; because both sight and touch confirm the testimony of smell. But how do we know that these sensations are something beside the impressions received in our soul? Why may we not believe them to come from some cause or other, without relation to external causes? Is it because other men say the contrary? Are we certain that they exist? How do they know what they tell us? How do we know that we hear rightly? There is the same difficulty with the other senses as with that of hearing, and if we doubt the testimony of three senses, why shall we not doubt that of four? Reasoning is here of no avail; it would lead us to cavils which would require an impassible doubt, and would tear from us a security, of which, notwithstanding all our efforts, we cannot despoil ourselves.
Moreover, if we appeal to the principles of reason, in order to prove the truth of sensation, we leave the territory of sensations, and do not place in them the primitive truth, origin of all other truths, nor accomplish what we undertook.
63. Hence it follows: First, that there is no one sensation which is the origin of the certainty of all others; this we have only indicated here, reserving the demonstration of it to our treatise on sensations. Secondly, although such a sensation were to exist, it could not serve as the basis of any thing in the intellectual order, for with sensation alone it is impossible even to think. Thirdly, that sensations, so far from being able to serve as the basis of transcendental science, cannot serve of themselves alone to establish any science; because necessary truths cannot flow from them, since they are contingent facts.(5)
CHAPTER VI.
TRANSCENDENTAL SCIENCE.—INSUFFICIENCY OF REAL TRUTHS.
64. We have thought proper briefly to refute Condillac's system, not on account of its intrinsic importance, or because it was not before in sufficiently bad repute, but in order to clear the field for higher and more strictly philosophical discussions. We should not omit to guard philosophy against the prejudice cast upon it by a system as vain as it is profitless. All that is most sublime in the science of the mind disappears with the statue-man and transformed sensations: we vindicate the rights of human reason by showing that before entering upon more transcendental questions it is indispensable to discard Condillac's system; just as it is necessary before making a good road to clear away the brushwood which obstructs the passage.
65. We come now to the proof that in the human intellectual order, such as it is in this life, there is no one truth the source of all truths; because no one truth includes them all.
Truths are of two kinds, real and ideal. We call facts, or whatever exists, real truths; we call the necessary connection of ideas ideal truths. A real truth may be expressed by the verb to be, taken substantively, or at least it supposes a proposition in which this verb has been taken in this sense: an ideal truth is expressed by the same verb taken copulatively, as signifying the necessary relation of a predicate with a subject, abstracting it, however, from both. We are, that is, we exist, expresses a real truth, a fact. Whoever thinks exists, expresses an ideal truth, for it does not affirm that there is any one who thinks or exists, but that if there is any one who thinks, he exists; or, in other words, it affirms a necessary relation between thought and being. To real truths corresponds the real world, the world of existences; to ideal truths the logical world, that of possibility.
The verb to be, is sometimes taken copulatively, although the relation expressed by it be not necessary: such is the case with all contingent propositions, and when the predicate does not belong to the essence of the subject. Sometimes the necessity is conditional, that is, it supposes a fact; and then there is no absolute necessity, since the supposed fact is always contingent. When we speak of ideal truths, we refer to those that express an absolute necessary relation, abstracting it from all order of existence; and on the other hand, we understand by real truths all those that suppose a proposition in which a fact has been established. To this class belong the truths of natural science, for they all suppose some fact which is the object of observation.
66. No real finite truth can be the origin of all others. Truth of this kind is the expression of a particular contingent fact, and consequently can neither include other real truths or the world of existences, nor ideal truths which refer only to necessary relations in the world of possibility.
67. Were we to see intuitively infinite existence, cause of all existences, we should know a real truth, origin of all others; but as we know this infinite existence only by discursion and not by intuition, it follows that we do not know the fact of that existence in which the reason of all other existences is contained. Neither is it possible for us, after having by means of discursion reached this cognition, to explain from this point of view the existence of the finite by the sole existence of the infinite; for if we abstract the existence of the finite, the discursion, by which we attained to the cognition of the infinite, disappears, and then our whole scientific fabric tumbles to the ground. Demonstrate to a man by means of discursion the existence of God, and require him, setting aside the point of departure, and depending upon the sole idea of the infinite, to explain not only the possibility, but also the reality of creation; and he cannot do it. If he only sets aside the finite all his reasoning fails, and no effort can prevent its failing; he is like an architect who, after having built a superb cupola, is required to support it although the foundations of the edifice are removed.
68. Take any real truth whatever, the plainest and most certain fact, and yet we can derive nothing from it if ideal truth comes not to fecundate it. We exist, we think, we feel; these are indubitable facts, but science
