Natural Light, Hypothetico-Deductivism, and Formal Logic
In this essay, I will argue that the certainty and the reliability of natural light ground Descartes hypothetico-deductive method, and this in turn shapes Descartes’ rejection of formal logic.
When discussing causes in the third Meditation, Descartes argues that ‘it is obvious by the natural light that the total cause of something must contain at least as much reality as does the effect’. (Descartes 12) When considering empirical questions and others[1], Descartes consults the natural light, or merely listens to what it says to him in a way similar to Socrates’ daemon[2], and draws a ‘vivid and clear’ intuition straight from this source; ‘(t)hings that are revealed by the natural light—for example, that if I am doubting then I exist—are not open to any doubt’. (9) While I’ll go into what it is about the natural light that makes it reliable for Descartes later, it should be noted now that Descartes’ affinity for natural light is very much related to his critique of the senses; Descartes thought of the senses as providing ‘at best, “a spontaneous impulse” to believe something, an impulse we’re able to resist’. (SEP section 5.1) For Descartes, one can logically doubt their senses insofar as they cannot know they are not dreaming, and therefore there is no absolute certainty to be derived from experience or granted to experience. On the other hand the natural light provides one with inherently indubitable truths;‘“(w)hatever is revealed to me by the natural light — for example that from the fact that I am doubting it follows that I exist, and so on — cannot in any way be open to doubt.”’ (Ibid.) Therefore, while experience can be logically subject to doubt, intuitions that are derived from natural light are indubitable.
For the sake of clarity, The argument goes like this:
1. Any belief B, where B is any empirical belief, can be logically doubted.
2. If a belief B can be logically doubted, then B cannot provide one with absolute certainty.
3. No belief B can provide one with absolute certainty. (2,1 MP)
This is connected to Descartes hypothetico-deductivism insofar as, as he states in the first Meditation, he wants to ground science on certain/incorrigible foundations; ‘"(b)y a method," wrote Descartes, "I mean certain and simple rules, such that, if a man observe them accurately, he shall never assume what is false as true, and will never spend his mental powers to no purpose."’(Passmore 546)
As stated above, one is said to have ‘(t)hings (...) revealed by the natural light’; namely intuitions. (SEP section 5.1) These intuitions are used to form hypotheses/propositions, which are then assessed via deduction. The method is grounded epistemically through this very natural light; there is no doubt for Descartes about this: if an intuition arises from natural light, it is given epistemic privilege. Thus, natural light goes hand in hand with Descartes’ goal to establish an absolute method for science, and shapes the way he crafts his hypothetico-deductive method.
While this shows how Descartes uses the natural light to ground his hypothetico-deductive method epistemically, it does not provide an account of just how this method is not merely epistemologically reliable but also ontologically reliable. How is this so? It is fair to say that there is nothing implicit about the theological underpinnings of Descartes’ natural light; these underpinnings are quite explicit, and I would argue they are what provides natural light with not only epistemic reliability, but also its metaphysical reliability. There’s a sense in which this is an intensely circular argument, but one can appreciate the reasoning a bit more if one considers the justification natural light provides to be epistemic insofar as it causes indubitably, and the justification Descartes’ concept of God provides to be metaphysical. What do I mean by this?
If one entertains a ‘vivid and clear’ intuition, then one is right to say that it is indubitable epistemically; one cannot help but doubt it, and must assume it to be knowledge. (Descartes 9) However, saying that one can’t help but to believe something only really states a psychological state or attitude one has in relation to a proposition; when in a dream, one can’t help but assume its truth, but this can be shown to be unsound if one wakes up and realises there was in fact no world there to have knowledge about. That is why Descartes must find something that cannot be doubted, but that is also ontologically independent of his mind; something he can latch onto, by virtue of reason alone, that can provide him with something more than mere belief. He finds his answer in the definition of God; God must exist because existence is a perfection and God, as the most perfect conceivable being, has all of the perfections. Descartes has knowledge of God by virtue of natural light, and can deduce something from the very concept GOD. Thus while Descartes himself comes to have knowledge of God from reason alone, he can be sure that his existence is not doubtable in the sense that experience would be because of dreams; the mind did not create God, it had an innate notion of him, and by virtue of intuitions drawn from about the concept, one can be sure that he exists independently of one’s ability to know him because of his nature; one can be sure of the metaphysical reliability of natural light..
How does this ground all of the intuitions drawn from natural light? Now that Descartes has deduced the existence of God from reason alone, he can use this ‘vivid and clear’ intuition to show that all things that arrive from the natural light must be true; ‘this shows clearly that it is not possible for him to be a deceiver, since the natural light makes it clear that all fraud and deception depend on some defect.’ (Descartes 9) If concepts are ‘seeds planted by God in our heads’, then the above statement implies that they cannot lead to deception; it follows from the definition of God that he cannot deceive. Thus, there are two foundations to natural light: 1) indubitability of God’s existence, and b) the idea that God does not deceive.
How does this discussion relate to Descartes' criticism of formal logic? According to Passmore, Descartes’ criticism of formal logic was centered around the idea that it was a non-ampliative process; while the ‘art of thought’, the art of introspecting and deducing ‘vivid and clear’ ideas, was grounded in the natural light and therefore one could learn something new from it, formal logic was (at the time) an external apparatus that Lull and others used to classify what was already known. (Passmore 549) While natural light does provide one with new information that one can know to be certain, “‘the traditional formal logic (...) does not provide us with such a method’ insofar as it is ‘better in explaining to others things that one knows (...) than in learning what is new"’ (Ibid.) I would argue that what underlies their criticism is the notion that natural light is something that can provide one with novel information, and that an external apparatus like formal logic distances human beings from their natural source of knowledge. As Passmore quotes De Morgan: logic ‘bound(s) the human mind: for the human mind, he has been implicitly instructed, is rapid and vigorous in abstract science, if only it take care to follow no leader." (550)
The natural light should be seen as the individual and society's basis for a common and scientific rationality, and it has this form within Descartes’ hypothetico-deductivism. His use of the concept grounds his methodology, and also shapes his critique of logic insofar as logic is seen as drawing human beings away from the knowledge that God has provided them.
Work Cited:
Brickhouse, Thomas C., and Nicholas D. Smith. The trial and execution of Socrates: sources and controversies. New York: Oxford University Press, 2002. Print.
Descartes, Rene. Translated by: Bennett, Jonathan. Meditations on first philosophy. April 2007.
Newman, Lex, "Descartes' Epistemology", The Stanford Encyclopedia of Philosophy (Fall 2010 Edition), Edward N. Zalta (ed.), URL=<http://plato.stanford.edu/archives/fall2010/entries/descartes-epistemology/>.
Passmore, J.A. Descartes, The British Empiricists, and Formal Logic. Philosophical Review, Vol. 62, No. 4 (Oct., 1953), pp. 545-553
[1] When arguing for God’s existence as well; ‘This shows clearly that it is not possible for him to be a deceiver, since the natural light makes it clear that all fraud and deception depend on some defect.’ (pg)
[2] “Socrates’ ‘divine sign’, that mysterious inner voice which from time to time warns him off something he is about to do’. (136 Brickhouse and Smith)
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