Reply to some objections

The first rule in the preceding chapter will not please everyone.

It will displease those imaginary scholars who claim to know everything and who never know anything, who take pleasure in speaking boldly about the most difficult things, and who certainly do not know the easiest.

They will say, with Aristotle, that:

• it is only in mathematics that one must seek complete certainty; but that morals and physics are sciences in which mere probability suffices
• Descartes was wrong to want to treat physics like geometry, and this is why he did not succeed
• it is impossible for men to know nature
• Nature’s mechanisms and secrets are impenetrable to the human mind

I would very much like to beg these gentlemen to speak no more of what they themselves admit they do not know; and to stop the ridiculous movements of their vanity, by ceasing to compose such large volumes on subjects which, by their own admission, are unknown to them.

But let these persons examine seriously whether it is not absolutely necessary either to fall into error, or never to give full consent except to entirely evident things: whether truth does not always accompany geometry, because geometers observe this rule; and whether the errors into which some have fallen regarding the quadrature of the circle, the duplication of the cube, and some other very difficult problems, do not come from some precipitation and some obstinacy, which made them take probability for truth.

Let them also consider, on the other hand, whether falsity and confusion do not reign in ordinary philosophy. Because philosophers content themselves with a probability very easy to find, and so convenient for their vanity and their interests. Do we not find almost everywhere an infinite diversity of opinions on the same subjects, and consequently an infinity of errors? Nevertheless, a very great number of disciples let themselves be seduced, and submit blindly to the authority of these philosophers, without even understanding their opinions.

It is true that there are some who recognize, after twenty or thirty years of wasted time, that they have learned nothing from their readings, but it does not please them to tell us so with sincerity. They must first prove in their own fashion that one can know nothing, and then afterward they confess it, because then they believe they can do so without anyone mocking their ignorance.

One would nevertheless have enough reason to be amused and to laugh at them, if one were to make skillful inquiries about the progress of their fine erudition; and if they were in the mood to declare to us in detail all the fatigues they have endured to acquire it.

But although this learned and profound ignorance deserves to be ridiculed, it seems more fitting to spare it and to have compassion for those who have consumed so many years to learn nothing, than for this false proposition, the enemy of all science and all truth, that one can know nothing.

Since, then, the rule I have established is so necessary in the search for truth, as we have just seen, let no one find fault with my proposing it. And let those who do not wish to take the trouble to observe it at least not condemn so illustrious an author as M. Descartes, because he followed it or made every effort to follow it. They would not condemn him so boldly if they knew the one of whom they pass so rash a judgment, and if they did not read his works as fables and romances, which one reads for amusement, and on which one does not meditate for instruction. If they meditated with this author, they would still find within themselves some notions and some seeds of the truths he teaches, which could develop despite the inconvenient weight of their false erudition.

The master who teaches us inwardly wants us to listen to him rather than to the authority of the greatest philosophers; he takes pleasure in instructing us, provided we are attentive to what he says to us. It is through meditation, and through very exact attention, that we question him, and it is through a certain inner conviction, and through those secret reproaches he makes to those who do not yield to them, that he answers us.

One must read the works of men in such a way that one does not expect to be instructed by men. One must question Him who enlightens the world so that He may enlighten us along with the rest of the world; and if He does not enlighten us after we have questioned Him, it will doubtless be because we have questioned Him badly. Whether one reads Aristotle, therefore, or whether one reads Descartes, one must not believe either Aristotle or Descartes at first; but one must only meditate as they did or as they ought to have done, with all the attention of which one is capable, and then obey the voice of our common master, and submit in good faith to inner conviction and to those movements one feels while meditating.

It is after this that one is permitted to form a judgment for or against authors. But it is after having thus digested the principles of the philosophy of Descartes and of Aristotle, that one rejects the one and approves the other; that one can even assert of the latter that one will never explain any phenomenon of nature by the principles particular to him, just as they have served no purpose for two thousand years, although his philosophy has been the study of the most able people in almost all parts of the world; and that, on the contrary, one can say boldly of the other that he has penetrated what seemed most hidden from the eyes of men, and that he has shown them a very sure path to discover all the truths that a limited understanding can comprehend.

But, without dwelling on the opinion one may have of these two philosophers and of all the others, let us always regard them as men, and let the followers of Aristotle not find fault if, after having walked for so many centuries in darkness, without finding themselves more advanced than before, one finally wants to see clearly what one is doing, and if, after having allowed oneself to be led like the blind, one remembers that one has eyes with which one wants to try to guide oneself.

Let us therefore be fully convinced that this rule — that one should never give full consent except to things one sees with evidence — is the most necessary of all rules in the search for truth; and let us admit into our minds as true only what appears to us with the evidence it demands. We must be persuaded of this in order to rid ourselves of our prejudices; and it is absolutely necessary that we be entirely delivered from our prejudices in order to enter into the knowledge of truth; because the mind must absolutely be purified before being enlightened: Sapientia prima stultitia caruisse (The first wisdom is to have been free from folly).

Remarks on the necessity of evidence

I am not speaking here of matters of the law that evidence does not accompany, like the natural sciences, the reason for which seems to be that we can perceive things only through the ideas we have of them. Now God has given us ideas only according to the needs we had of them to guide ourselves in the natural order of things, according to which He created us. So that the mysteries of faith, being of a supernatural order, one must not be surprised if we do not have evidence of them, since we do not even have ideas of them: because our souls are created by virtue of the general decree, by which we have all the notions that are necessary for us, and the mysteries of faith were established only by the order of grace which, according to our ordinary manner of conceiving, is a decree posterior to this order of nature.

One must therefore distinguish the mysteries of faith from natural things. One must submit equally to faith and to evidence; but in matters of faith one must not seek evidence, just as in natural things one must not stop at faith, that is to say, at the authority of philosophers. In a word, to be faithful one must believe blindly, but to be a philosopher one must see evidently.

One agrees, nonetheless, that there are still truths besides those of faith, of which one would be wrong to demand incontestable demonstrations, such as those concerning historical facts, and other things that depend on the will of men. For there are two kinds of truths: some are necessary and others contingent. I call necessary truths those that are immutable by their nature and those that have been established by the will of God, which is not subject to change. All others are contingent truths. Mathematics, metaphysics, and even a great part of physics and morals contain necessary truths. History, grammar, particular law or customs, and many others that depend on the changeable will of men, contain only contingent truths.

It is therefore demanded that one observe exactly the rule just established in the search for necessary truths, the knowledge of which can be called science; and one must be content with the greatest probability in history, which includes contingent things. For one can generally call by the name of history the knowledge of languages, customs, and even that of the different opinions of philosophers, when one has learned them only by memory and without having had evidence or certainty of them.

The second thing to be noted is that in morals, politics, medicine, and in all the sciences that are practical, one is obliged to content oneself with probability — not forever, but for a time; not because it satisfies the mind, but because necessity presses, and if one waited to act until one were fully assured of success, the opportunity would often be lost. But although it happens that one must act, one should in acting doubt the success of the things one executes, and one must try to make such progress in these sciences that one can on occasion act with more certainty; for this ought to be the ordinary end of study and of the employment of all men who make use of their minds.

The third thing, finally, is that one must not absolutely despise probabilities, because it ordinarily happens that several, joined together, have as much force to convince as very evident demonstrations. There are an infinity of examples of this in physics and in morals, so that it is often fitting to amass a sufficient number on subjects that cannot be demonstrated otherwise, in order to be able to find the truth that it would be impossible to discover in any other way.

The law I impose is quite rigorous, that an infinity of people will prefer never to reason at all rather than to reason on these conditions; that one will not run so fast with such inconvenient circumspections. But it must also be granted to me that one will walk with safety in following it; that up to now, for having run too fast, one has been obliged to retrace one’s steps; and even a great number of persons will agree with me that, since M. Descartes discovered in thirty years more truths than all the other philosophers, because he submitted to this law; if several persons were to philosophize as he did, one could in time know most of the things that are necessary for living happily, as far as one can on a earth that God has cursed.