Descartes and the Rationalists

René Descartes (1596 - 1650)

Certain revolutions in philosophy happen with a bang not a whimper. That is to say, their architects are self-aware game-changers, fully cognisant of their critical role in history, and proclaim their revolution unapologetically. Such was the case with Kant, who foresaw the impact of his ‘Copernican’ idealism, and Wittgenstein, who famously declared that, after him, there would be no further need for philosophy. René Descartes (1596 – 1650) belongs among these happy few. With his Discourse on Method (1637), Descartes turned on their head certain basic assumptions that had dominated the Medieval mindset, and ushered in a new era of philosophical inquiry – and he did it knowingly.

 Where for over a thousand years, human reason had been looked down on by theologians, deemed flawed and subservient to divine wisdom, Descartes lay it at the very centre of his epistemology. Reason is the source of all unequivocal truth, he would boldly argue – so long as it is wielded well, according to a fool-proof method. Though intuitive to the modern mind, this assertion had, for Descartes’ contemporaries, all the force of a hurricane, and swept through the intellectual landscape leaving much upended. For the first time since the pre-Christian era, man had autonomy of inquiry; finally liberated from the shackles of dogma and superstition, he was now free to understand the nature of the world around him. And all the tools he needed to accomplish this seemingly impossible feat were to be found within.

 Descartes’ rationalistic revolution didn’t exactly come from nothing. Before him, Galileo Galilei (1564 – 48) had applied a deductive methodology to further his understanding of astronomy. Francis Bacon (1561 – 1626), generally considered the first empiricist, had argued for an understanding of nature based on rational inductions from sense observation. Pico della Mirandola (1463 – 94), a father of Italian humanism, had suggested that, if we exercised our reason, we could ascend to the ranks of angels[1]. The power of reason had been many times implied but never thoroughly and painstakingly demonstrated. With Descartes, there was a complete overhaul; a total destruction of the old and its systematic replacement with the new. Reason was the new logos, the new pathway to truth and enlightenment.

 The first thing that impresses the reader of Descartes’ Discourse – and his Meditations, for that matter – is his self-awareness as an iconoclast. The first pages of both works abound with unashamed references to the ambitious scope of his work, and the completeness of its upending of outmoded ways of thinking. His radical ‘cast-down-the-idols’ mindset is evident from the outset, when he makes the sweeping declaration that, having familiarised himself with all the established learning available to a man of his time, he had found nothing in it of real substance: 

…I compared the disquisitions of the ancient moralists to very towering and magnificent palaces with no better foundation than sand and mud... [2] 

None of the greats had got it right – not Aristotle, not Aquinas, not Augustine, not even Plato with whom Descartes would likely have agreed on many points. They all provide flawed conceptions of reality, incomplete appraisals of the nature of knowledge, and wildly ineffective methods for arriving at truth. Their conclusions, ‘towering’ and ‘magnificent’ though they may be, are ultimately built on muddy premises and destined to crumble.

Descartes was only too glad to hurry this process along, to lay the dynamite at the base of this wondrous, unstable edifice and press ‘detonate’. Humanity had for too long been plagued by a fatal flaw: a pernicious combination of hubris and ignorance. The world is divided in two categories of men, according to Descartes. The first are those men who are so sure of their powers, that they “are precipitate in their judgments and want the patience requisite for orderly and circumspect thinking.” The second are those who, lacking either the intellect or the self-assuredness to have opinions of their own, prefer to defer to the opinions of the first[3].

For Descartes, there are no two ways about it: men are, for the most part, bad thinkers – even those who are certain they aren’t. And not even those few philosophers history has come to deem ‘great’ are exempted, for just as they are capable of the highest degree of excellence, “they are equally open to the greatest aberrations[4].” The higher they leap, the harder they are likely to fall – so to speak.

The corpus of cultural mores and mathematical truths are no use to us either: the first, because they are arbitrary and change from one land to the next; the second, because they are so abstruse that they are all but inaccessible to the average man.  

Having discarded all traditional fonts of knowledge, Descartes comes to the radical conclusion that he must rid himself of all his prior opinions, or as he words it, ‘demolish everything’. Since, for one reason or another, all information he’s hitherto acquired about the world can be deemed unreliable – either because he originally imbibed it from a thinker who reputed his method more sound than it in fact was, or because it was handed down to him by arbitrary custom – Descartes surmises that all his old beliefs can be doubted, without exception.

‘Cartesian doubt’, as it would come to be known, is in fact the cornerstone of this rationalist’s approach.  Question everything that that can be questioned (in other words, practically everything). Subject to the most rigorous scrutiny every item of knowledge you assume to be factual, every custom you’ve inherited, every theological concept you’ve been taught – even, and perhaps especially those ‘truths’ you’re least inclined naturally to question – so that you can start over, and build your new philosophical edifice from the ground up.

The more assiduous reader will now wonder how any philosophical edifice – particularly one with the sturdy structure Descartes is aiming for – could be built in a world in which most everything can be doubted. Descartes’ answer to this conundrum is where his revolution really gets going. Everything can be doubted, he argues, except one thing; the act of my doubting itself[5]. For even when I doubt that I doubt, I am in fact affirming doubt by negating it. And since doubt is but a form of thought, if I’m doubting, I’m thinking. And if I’m thinking, then there must necessarily exist an ‘I’ that is doing the thinking. I am thinking thing, a res cogitans [6]. I know I exist because I know I think or, in Descartes’ immortal phrasing, “I think therefore I am[7].”

 So if it is beyond doubt that I think, Descartes proclaims, then this is where I shall start my grand project. I shall start with the act of thinking itself, with my ability to think things through ‘purely’, in a way untainted by superstition, fallacy, hubris, cultural commonplace or ideology. I shall build my edifice on that solidest of foundations: reason.

 The ‘natural light of reason’[8] is what Descartes calls it, and the metaphorical wording here is telling. For centuries, medieval theologians had been describing Jesus, the logos using similar language. He was the ‘light which enlightens everyone’[9]; that guiding principle by means of which god’s mysteries were illuminated. For Descartes, man’s reason has precisely this function. It casts its light over darkness, ‘illuminating’ truths that have hitherto remained hidden to us, obscured by our unfortunate susceptibility to error.

 In the Cartesian paradigm, reason occupies a position of absolute supremacy. It is a universal faculty, so everyone possesses it[10]. It is a ‘spontaneous, natural impulse’[11], meaning we are endowed with it already at birth and cannot help exercising it. It is the most reliable pathway to truth[12], and nothing lies beyond its reach[13]. Unlike the senses, which can easily deceive us, reason will not lead us astray – provided, that is, we use it correctly.

 And here lies the rub. The reason why countless historical greats had got it wrong was that they had been thinking poorly. God is infinitely good, so he would never encumber us with dysfunctional parts[14]. If we err, as we often do, the blame lies, not with the machinery, which is impeccably crafted, but its operators. When contemplating the nature of reality, the ancients had thus made the error of failing to apply sufficient scrutiny to muddy ideas, and then gone on to derive conclusions that – no surprise – turned out just as erroneous as their premises. They had, in other words, failed to exercise reason the proper way, the way god intended.

 One might now ask what the ‘proper way’ to reason is. And though he could very well have left this problem to posterity to solve, Descartes valiantly confronts it head on. The four-step process he outlines, in the Discourse, for determining truth is now known as the ‘Cartesian method.’ I won’t number all four steps here, but the crux of it is this: to begin with, you must cast all forms of knowledge from your mind except those ideas that are so clear and distinct as to leave no room for doubt whatsoever. Begin your line of reasoning with one such clear and distinct idea (an axiom), then proceed as carefully as possible, step by step, from simpler to more complex ideas until you have achieved the desired conclusion, taking care never to miss even a small step along the way.

 There we have it. In two relatively short philosophical works, Descartes achieved at least three epistemological breakthroughs. He did away with all accepted knowledge and provided convincing justifications for doing so; he established human reason as the sufficient font for the attainment of truth; and he meticulously outlined a method one could use in order to wield reason to this very end.

Baruch Spinoza (1632 - 1677)

Descartes’ method would prove entrancing to history’s next great rationalist, Baruch Spinoza (1632 – 1677). So much so, in fact, that Spinoza would use it for the purpose Descartes had intended: to build his grand philosophical edifice from the ground up. When you read his Ethics (pub. 1677), this is immediately perceptible. Spinoza begins the work with a series of palpably Cartesian axioms. These serve as mathematical first principles, clear and distinct ideas upon which, as his tome unfolds, he builds upon slowly and incrementally. The propositions he presents the reader are derived from and refer directly to the axiomatic principles he sets out with, and he approaches their verification as Descartes had recommended: slowly and meticulously, taking great care never to skip a step.

 The conclusions his method leads to are as inspired as his proofs are dry and fastidious. What Spinoza is best known for is his theory of substance, which differs substantially from Descartes’ and also, for different reasons, from Leibniz’, which we shall examine next. Unlike Descartes, who believes in the fundamental difference between mind, which is supreme and animated by reason, and body, which is perishable and dependent on the senses, Spinoza is a monist. Essentially, this means he believes that the cosmos is composed of only one substance.

For Spinoza, the universe and all things in it are god, and he uses a series of serpentine arguments to arrive at this unintuitive conclusion. He begins by postulating that if two things have nothing in common, one could not possibly be the cause of the other.[15] If this is the case, then it must follow that one substance cannot produce another substance, and therefore “cannot be produced by anything external to itself.”[16] 

 Spinoza, who until this point has said nothing particularly unsettling, delivers his coup de grace. Every substance, he posits, must by necessity be infinite, for if it weren’t, “it would then be limited by something else of the same kind, which would also necessarily exist; and there would be two substances with an identical attribute, which is absurd. It therefore exists as infinite.” Substance is infinite and indivisible, and since god is infinite and indivisible, the two must perfectly coincide:

 As God is a being absolutely infinite, of whom no attribute that expresses the essence of substance can be denied, and he necessarily exists; if any substance besides God were granted, it would have to be explained by some attribute of God, and thus two substances with the same attribute would exist, which is absurd; therefore, besides God no substance can be granted, or, consequently, be conceived.[17] 

 And herein lies Spinoza’s own little revolution. Since there is no substance but god, god is in everything and everything in existence partakes in him – including me and you. We are all god, or at least manifestations thereof. The heretical implications of this Pantheistic monism, which are would eventually would lead to Spinoza’s excommunication from Amsterdam’s Jewish congregation, are stark, as are those of his epistemology.

 If, since god is in everything, he’s also in me, it must mean that I am at one god and with all that is around me; I am at one with nature. And if, substantially, I am at one with nature it presumably means that I am poised to understand it. This would be Spinoza’s assertion both in the Ethics, were he argues that “the human mind has adequate knowledge of the nature of god”[18], and his more explicitly religious work, the Tractatus Theologico-Politicus, where he elaborates it more fully. Here, he uses language borrowed from Descartes to assert the supremacy of human reason over scripture: “The light of nature is a more excellent way to understand god than words.”[19]

 According to Spinoza we are all born prophets, endowed by nature with certain faculties that allow us to understand the true essence of things. We thus have no real use for divine revelation. Our own inborn understanding is our scripture, or as Spinoza words it, “Natural knowledge is prophecy.”[20] If we exercise our reason in the specific way Descartes pioneered and Spinoza himself employed in his proofs, we should have no need, for our comprehension of the universe and all its phenomena, of any other tool than our minds.

 This is an exact reversal of the medieval conception, which operates according to the contrary principle: scripture trumps reason every time.[21] It is also distinct from the sense-dependent position of the empiricists, for whom all knowledge derives, not from reason but from experience. In a way, Spinoza’s pantheistic theory of knowledge presages the stance of the nineteenth-century idealists, who argued that, since the outer world of objects and our inner world of ideas were one and the same, true understanding of reality “comes from within.”[22]

Gottfried Leibniz (1646 - 1716)

The last of the three major seventeenth-century rationalists is Gottfried Leibniz (1646 – 1716). Leibniz’ major affirmations in support of the supremacy of reason are largely worded as rebuttals to the empiricism of John Locke (1632 – 1704). In his New Essays on Human Understanding, in fact, Leibniz picks apart, one by one, the arguments Locke sets out in his Essay Concerning Human Understanding (1869), and arrives at conclusions not too dissimilar to Descartes’ and Spinoza’s.

 Leibniz begins his Essays by declaring himself a Platonist sympathiser.[23] Like Plato, he believes in the innateness of all ideas [24], and the ability of reason to ‘tease them out’ of the subconscious. For Leibniz, entire realms of human knowledge are necessarily innate, including geometry, arithmetic and even morality.[25] Although he’s gracious enough to concede, here and there, that sense perception plays a part, albeit small[26], in our understanding of the world, for him there is no question: reason is the font of the only knowledge that really counts. Only reason is capable of establishing general rules[27], mathematical certainties[28] and what he calls ‘intellectual ideas’, his own version of Descartes’ ‘clear and distinct ideas’ from which all necessary truths spring[29].

 Leibniz structures his arguments in opposition to Locke’s. Where Locke would claim that if ideas were innate, they would have to be universal, Leibniz retorts that universality is no argument for innateness to begin with[30]. A belief’s “being rather generally accepted among men” (i.e. its universality) is merely an indication, rather than proof that it is innate[31]. A principle is proven only when its “certainty comes from within us.”[32] We need not rely on its being held to be true be all men.

 Leibniz then turns his attention to Locke’s refutation of subconscious knowledge. If an idea is innate, then when an individual learns it, it must mean the idea had lain dormant and unattended before it registered in his consciousness, but it would be absurd to argue that a soul could possess ideas that it doesn’t consciously perceive[33]. To this Leibniz confidently retorts: we know “an infinity of things we are not aware of all the time; it is the function of memory to store them, and of recollection to put them before us again.”[34] It is quite evidently possible, in other words, for us to possess ideas without knowing we posses them.

 Finally, he tackles Locke’s most memorable argument: if there were such a thing as an innate idea, even children and simpletons would possess it, and there is patently no such idea[35]. Leibniz’ counter-attack here is clever. Innate ideas make their appearance in the conscious mind only if due attention is paid to them. Since children and simpletons lack the mental space to devote to anything other than their bodily needs, it is easy to see how they might overlook such ideas even though they are, in fact, there. Innate ideas are just as present in children’s minds as they are in ours, they just lack the requisite skills to draw them out.[36]

 Like Spinoza Leibniz was a monist, but of an entirely different kind. He believed in ‘monads’, simple substances that constitute the building blocks of reality. These exist in degrees and are subject to change[37]. For Leibniz the each monad is a soul, and the reasoning he provides for this belief goes as follows: Descartes had claimed that extension is an attribute of matter, but this cannot be true. A substance cannot be extended, for this would involve a plurality, and reality would therefore amount to an aggregate of substances. Each substance is therefore unextended, and reality is comprised of infinite variety of substances (monads). Each monad, therefore is, not extended, physical matter, but an unextended soul. According to Bertrand Russell, this leads Leibniz do deny the existence of matter and propose thought as the one, universal substance.

 Descartes, Spinoza and Leibniz: three philosophers with radically different conceptions of substance, but united in their exultation of reason as the supreme means of arriving at the truth of reality.

[1] Mirandola, Pico della. Oration on the Dignity of Man, loc. 2865: “If [man] cultivates his intellectual seeds, he will be an angel and a son of God.”

[2] Descartes, René. Discourse on the Method (DSM), Part I, p. 6

[3] Ibid.

[4] Ibid. Part 1, p. 2

[5] Ibid. Part IV, p. 25)

[6] Descartes. Meditations, p. 18

[7] DSM Part IV, p. 25

[8] Meditation III, p. 26

[9] John Ch 1: 9

[10] DSM Part I, p. 2

[11] Meditation III, p. 26

[12] Ibid.

[13] DSM Part II, p. 15

[14] Meditation IV, p. 37

[15] Spinoza. Ethics, p. 51

[16] Ibid., p. 65

[17] Ibid., p. 184

[18] Ibid., loc. 1249

[19] Spinoza. Tractatus theologico-politicus, loc. 529

[20] Ibid., loc. 512

[21] Aquinas, Thomas. Summa Contra Gentiles: Book 1.7

[22] Schopenhauer, Arthur. The World as Will and Representation, Book 2, Ch. 17

[23] Leibniz, Gottfried. New Essays on Human Understanding, p. 49

[24] Ibid., p. 69-70

[25] Ibid., pp. 72 & 85

[26] Ibid., pp. 51 & 72

[27] Ibid., p. 52

[28] Ibid., p. 50

[29] Ibid., p. 75

[30] Ibid., p. 70

[31] Ibid., p. 71

[32] Ibid.

[33] Locke, John. Essay Concerning Human Understanding, p. 27

[34] Leibniz. New Essays, p. 72

[35] Locke. Essay, p. 27

[36] Leibniz. New Essays, p. 81

[37] Leibniz. Monadology, sec. 396