A Brief Note on Descartes, Eternal Truths, and Rationality

     Copyright 2014 Bruce W. Hauptli

The picture of Descartes which I have been drawing—one according to which he is a consummate rationalist (who believes that “what is real is rational, and what is rational is real”)--needs at least two qualifications.  For Descartes there is a class of truths called “eternal truths”—included here would be all those “innate and a priori truths whose denials are contradictions.  In his Principles of Philosophy [1644] he characterizes these as follows:

[We must now talk of what we know as eternal truths.]
  When we apprehend that it is impossible that anything can be formed of nothing, the proposition ex nihilo nihil fit is not to be considered as an existing thing, or the mode of a thing, but as a certain eternal truth which has its seat in our mind, and is a common notion or axiom.  Of the same nature are the following: ‘It is impossible that the same thing can be and not be at the same time’, and that ‘what has been done cannot be undone,’ ‘that he who thinks must exist while he thinks,’ and the very many other propositions the whole of which it would not be easy to enumerate.1 

These, surely, are to be amongst the most secure of his “truths,” and are to be knowable, certain, and, ultimately, indubitable (of course these may be redundant, at least in part, but all three bring to light important elements of these truths).  While he may “doubt” them, such a “methodological doubt” is supposed to ultimately display their status as known, certain, and indubitable. 

     As we learn in the “Third Meditation,” however, this “certainty” may well have to await a proof of his deity’s existence (and that deity’s benevolence), but, surely, given this these truths are guaranteed—aren’t they?  Here the “first qualification” comes in.  In his “Reply to Objections II,” Descartes maintains:

that an atheist can know clearly that the three angles of a triangle are equal to two right angles, I do not deny, I merely affirm that, on the other hand, such knowledge on his part cannot constitute true science, because no knowledge that can be rendered doubtful should be called science.  Since he is, as supposed, an Atheist, he cannot be sure that he is not deceived, in the things that seem most evident to him, as has been sufficiently shown; and though perchance the doubt does not occur to him, nevertheless it may come up, if he examines the matter, or if another suggests it; he can never be safe from it unless he first recognizes the existence of a God.2 

Similarly, near the end of the “Fifth Meditation” he says that:

…although I am of such a nature that as long as I understand anything very clearly and distinctly, I am naturally impelled to believe it to be true, yet because I am also of such a nature that I cannot have my mind constantly fixed on the same object in order to perceive it clearly, and as I often recollect having formed a past judgment without at the same time properly recollecting the reasons that led me to make it, it may happen meanwhile that other reasons present themselves to me, which would easily cause me to change my opinion, if I were ignorant of the facts of the existence of God, and thus I should have no true and certain knowledge, but only vague and vacillating opinions.  Thus, for example, when I consider the nature of a [rectilinear] triangle, I who have some little knowledge of the principles of geometry recognize quite clearly that the three angles are equal to two right angles and it is not possible for me not to believe this so long as I apply my mind to its demonstration; but so soon as I abstain from attending to the proof, although I still recollect having clearly comprehended it, it may easily occur that I come to doubt its truth, if I am ignorant of there being a God.   For I can persuade myself of having been so constituted by nature that I can easily deceive myself even in those matters which I believe myself to apprehend with the greatest evidence and certainty, especially when I recollect that I have frequently judged matters to be true and certain which other reasons have afterwards impelled me to judge to be altogether false. 
  But after I have recognized that there is a God—because at the same time I have also recognized that all things depend upon Him, and that He is not a deceiver, and from that have inferred that what I perceive clearly and distinctly cannot fail to be true—although I no longer pay attention to the reasons for which I have judged this to be true, provided that I recollect having clearly and distinctly perceived it no contrary reason can be brought forward which could ever cause me to doubt its truth; and thus I have a true and certain knowledge of it.3 

Now these passages suggest that what might be called an “epistemological schizophrenia” cuts very deeply indeed in the Meditations.  Early in the “Third Meditation,” Descartes maintains that:

…since I have no reason to believe that there is a God who is a deceiver, and as I have not yet satisfied myself that there is a God at all, the reason for doubt which depends on this opinion alone is very slight, and so to speak metaphysical.  But in order to be able altogether to remove it, I must inquire whether there is a God as soon as the occasion presents itself; and if I find that there is a God, I must also inquire whether He may be a deceiver; for without a knowledge of these two truths I do not see that I can ever be certain of anything.4 

This, of course is the genesis of what is called his “circularity problem.”5   It certainly appears that however “slight” the metaphysical doubt is, true (that is “scientific”) knowledge requires that not even such doubts are possible, and thus, at least for atheists such as me, even knowledge of the cogito may be “unavailable.”6 

     Without becoming a theist, it would seem eternal truths and, indeed, even the cogito are beyond my ken.  This, of course, means that I could not rely on knowledge of myself, and my nature, to prove the deity’s existence—and, thus, the “Third Meditation” proof for god will not suffice to legitimate my knowledge of eternal truths.  The most I can hope for, it would seem, is that I come to understand the proof in the “Fifth Meditation,” and, thus, remove the “metaphysical doubt.”7

     In short, it would seem as if atheists like me are condemned to the most serious possible Cartesian skepticism.  Rationality, then (and this is the “first qualification”) seems available only to theists.8   If this is truly his view, then it would appear that he has not provided as “new” an epistemological view as he is usually taken to provide.  Certainly to someone schooled as he was, Saint Augustine’s nisi credideritis, non intelligetis (unless you believe, you will not understand) seems to be suggested here.9   It appears that not only our knowledge of the external world, but our knowledge of mathematics, of the self, and all eternal truths, awaits the theological knowledge at the core of (his particular brand of) theism. 

     Now this qualification might not seem all that serious to some, because they conceive of Descartes’ deity as an essentially rational being—one who would no more countenance contradiction than deception.  Here the “second qualification” emerges however.  In his “Reply to Objections VI” Descartes maintains that:

to one who pays attention to God’s immensity, it is clear that nothing at all can exist which does not depend on Him.  This is true not only of everything that subsists, but of all order, of every law, and of every reason of truth and goodness; for otherwise God, as has been said just before, would not have been wholly indifferent to the creation of what he has created.  For if any reason for what is good had preceded his preordination, it would have determined Him towards that which it was best to bring about; but on the contrary because He determined Himself towards those things which ought to be accomplished, for that reason, as it stands in Genesis, they are very good; that is to say, the reason for their goodness is the fact that He wished to create them so.  Nor is it worth asking in what class of cause fall that goodness or those other truths, mathematical as well as metaphysical, which depend on God; for since those who enumerated the classes of cause did not pay sufficient attention to causality of this type, it would have been by no means strange if they had given it no name.  Nevertheless they did give it a name; for it can be styled efficient causality in the same sense as the king is the efficient cause of the laws, although a law is not a thing which exists physically, but is merely as they say [in the Schools] a moral entity.  Again it is useless to inquire how God could from all eternity bring it about that it should be untrue that twice four is eight, etc.; for I admit that that cannot be understood by us.  Yet since on the other hand I correctly understand that nothing in any category of causation can exist which does not depend upon God, and it would have been easy for Him so to appoint that we humans should not understand how these very things could be otherwise than they are, it would be irrational to doubt concerning that which we correctly understand, because of that which we do not understand and perceive no need to understand.  Hence neither should we think that eternal truths depend on the human understanding or on other existing things; they must depend on God alone, who, as the supreme legislator, ordained them from all eternity.10 

In short, the eternal truths depend (for their truth, etc.) on his deity, who could have made them untrue—that is to say, presumably, that this deity could have “made contradictions” (I am not sure that I can add ‘true’ here legitimately, though, presumably the only sense left to the term is “what the deity makes”).  As he says in a series of letters to Mersenne:

…the mathematical truths you call eternal truths have been established by God and depend entirely on him, just as much as all the rest of his creatures.  It is in fact to speak of God as of a Jupiter or Saturn, and to subject him to the Styx and the Fates, to say that those truths are independent of him.  Do not hesitate, I tell you, to avow and to proclaim everywhere, that it is God who has established the laws of nature, as a King establishes laws in his Kingdom.11 

…as for eternal truths, I say again that they are true or possible insofar as God knows them as true or possible, but not, on the contrary, known to be true by God as though they were true independently of him.  And if people understood properly the meaning of their words, they could never say without blasphemy that the truth of something precedes the knowledge that God has of it, for in God willing and knowledge are but one, in such a way that from the very fact that he wills something, he therefore knows it, and it is only for that reason that such a thing is true.  Thus we must not say that if God did not exist, nevertheless those truths would be true; for the existence of God is the first and most eternal of all the truths there can be, and the only one from which all the others flow.12 

You also asked what necessitated God to create the eternal truths.  And I say that he was just as free to bring it about that it is not true that all the lines drawn from the center to the circumference are equal, as he was not to create the world.  And it is certain that these truths are not more necessarily joined to his essence than are other creatures.  You ask what God has done to produce them.  I say that from the very fact that he willed and understood them from eternity, he created them, or rather (if you attribute the term created only to the existence of things), he established and made them.  For in God it is the same thing to will, to understand, and to create, without one of these taking precedence over the others, even by a distinction of reason.13 

Clearly his deity can not be “essentially” rational (assuming, that is, that a commitment to any and all of the above mentioned “eternal truths” is partially constitutive of rationality), while the status of the eternal truths is clearly to be found in this deity, it is not the case that they are necessary—they depend upon a free choice (and upon the fact that when he wills something, he knows it, and for that reason, it is true).  This is the “second qualification.”  For Descartes the “truth” of the eternal truths depends on an active exercise of his deity’s free will, one which is “not…necessarily joined to his essence” any more than is his act of willing any creatures.   That is to say, from Descartes’ perspective the truth of the eternal truths is no more guaranteed than the truth of my existence.  Both the existence (or truth) of this particular atheist and of the mathematical truths (about triangles, circles, and addition) depend upon his will

     Of course, if even the eternal truths depend upon his deity’s will, then absolutely nothing can be certain, justified, or rationally established until the existence of this deity is established and some understanding of the nature of this deity is reached.  This leaves us with a serious dilemma, however, since it appears that he wishes to advance a rational argument for the deity’s existence, and since he seems to appeal to an “eternal truth” to establish the benevolence of this deity (e.g., that “existence is a perfection”14 and that “deception is an imperfection”).  If he is to offer a proof here which will “remove” the metaphysical doubt, allow us to rely upon our memory, undergirds the clarity and distinctness of some of our ideas, and, thus, enable us to become legitimately certain; then this proof itself must either have a higher level of rational legitimacy than that available to eternal truths,15  it must have some other source of legitimacy than that which depends on reason and eternal truths, or it must be prone to a vicious epistemic circularity.

     While my difficulties here may, after all, be directly the result of the fact that as an atheist I can not ever attain full certainty, it does not seem plausible to me that Descartes can maintain that metaphysical doubt can not be removed until one has attained theological understanding, and offer a metaphysically indubitable rational proof (which relies upon eternal truths) to provide that theological understanding. 

Notes: (click on note number to return to the text for the note)

1 Rene Descartes, The Principles of Philosophy [1644], in The Philosophical Works of Descartes v. 1, eds. and trans. Elizabeth Haldane and G.R.T. Ross (Cambridge: Cambridge U.P., 1969), Part I, Principle 49, pp. 238-239. 

2 Rene Descartes, “Reply to Objections II,” [1641], in The Philosophical Works of Descartes v. 2, eds. and trans. Elizabeth Haldane and G.R.T. Ross (Cambridge: Cambridge U.P., 1970), p. 39. 

3 Rene Descartes, Meditations on First Philosophy [1641], in The Philosophical Works of Descartes v. 1, op. cit., pp. 183-184. 

4 Ibid., p. 159. 

5 Cf., Alan Gewirth, "The Cartesian Circle," Philosophical Review v. 50 (1941), pp. 368-395; and Edwin B. Allaire, "The Circle of Ideas and the Circularity of the Meditations," Dialogue v. 2 (1966), pp. 131-153. 

6 I am not sure how extensive the “schizophrenia” is for theists (of his particular stripe), but the passage from the replies clearly applies to “mathematical truths of geometry,” and the discussion in “Meditation III", leading up to the above claim clearly places “mathematical truths of arithmetic” in doubt, as well, arguably, as the cogito—especially for, it would seem, atheists. 

7 Of course, that proof only proves his deity necessarily exists, and I need to know both truths if I am going to get anywhere.  Presumably Descartes intends that his ontological argument will give “first” certainty not only of his deity’s existence but also of its nature, then.  Of course the more that this proof must do, the more it may come into question—but that is another story! 

8 Moreover, presumably, not just any theism will do—and of course, the theist must have knowledge of the deity’s existence and nature (benevolence). 

9 This much-quoted passage is from the Septuagint version of the Bible (from Isaiah, VII, 9).  Of course other versions translate the passage differently.  The King James Version has, "If you will not believe, surely ye shall not be established." 

10 Rene Descartes, “Reply to Objections VI,” [1641], in The Philosophical Works of Descartes v. 2, op. cit., pp. 250-251. 

11 Rene Descartes, Letter to Mersenne [April 15, 1630], trans. Marjorie Grene and Roger Ariew, in Rene Descartes: Philosophical Essays and Correspondence, ed. Roger Ariew (Indianapolis: Hackett, 2000), p. 28. 

12 Rene Descartes, Letter to Mersenne [May 6, 1630], trans. Marjorie Grene and Roger Ariew, in Rene Descartes: Philosophical Essays and Correspondence, op. cit.,  p. 29. 

13 Rene Descartes, Letter to Mersenne [May 27 1630], trans. Marjorie Grene and Roger Ariew, in Rene Descartes: Philosophical Essays and Correspondence, op. cit., p. 30. 

14 In “Meditation Five” this claim’s “truth” is clarified by appeal to a number of mathematical examples. 

15 Perhaps this is the “safest choice” for Descartes, and his rhetorical question, in “Meditation Five” which “asks” “for is there anything more manifest than that there is a God, that is to say, a Supreme being, to whose essence alone existence pertains?” [Rene Descartes, Meditations, op. cit., p. 183] certainly may seem to suggest that this particular truth has an “extraordinarily special epistemic status” above that of eternal truths and beyond the pale of metaphysical doubt.  To the extent that this “move” saves him, I would insist, he will need to assign similar status to at least one more claim: that deception is an imperfection—after all, he gets rid of the metaphysical doubt only when he has established both the existence and the “benevolence” of his deity.  Both elements of this “argument” must be beyond the pale of metaphysical doubt.  I find both claims dubitable however—without needing to reach as far as his “slight and metaphysical” doubts. 

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Last revised on: 09/09/2014