Excerpts from Science & Religion: Some Historical Perspectives (1991)

The Origins of Modern Skepticism

Excerpts from The Scientific Revolution (1998) By James R. Jacob

During the late sixteenth century . . . an intellectual movement was developing . . . This new current was a revival of an ancient skepticism that claimed that nothing can be known with certainty . . .

There were at least three developments that underwrote the skeptics’ argument: the Reformation, the overseas discoveries (especially in the New World), and the recent publication of certain ancient texts of skeptical philosophy. First, what was the effect of the Reformation? Catholics and Protestants alike looked to the Bible as the word of God and therefore the final authority in matters of faith. But both acknowledged that the Bible had to be properly interpreted in order for its truth to be revealed, and their approaches to this enterprise were fundamentally different. For centuries, the Catholics had held that the Bible must be read in the light of papal pronouncements and traditions established by church councils. But Protestants, beginning with Luther, now claimed that what conscience is compelled to believe on reading the Bible is true. Catholics quickly pointed out that if the Protestants had their way and individual conscience became the measure of truth, every man (or woman) could become his (or her) own church, and the result would be anarchy. Events, moreover, seemed to bear this argument out.

By the late sixteenth century, many parts of western Europe had paid a heavy price for religious dogmatism. Violence and terror had taken two forms—religious wars . . . [and] the witch-craze . . . The misery of the wars and the witch-craze produced, in some minds, a revulsion against the dogmatism and a growing skepticism about where truth could be found.

The second factor, working in the same direction, was the overseas voyages, which caused thinkers to see that truth is relative to culture, that what one people takes for good, beautiful, and true may be thought of as the reverse by another. Third, the newly available writings of Sextus Empiricus (fl. 200 AD) had their influence on the origins of modern skepticism. Sextus’s writings are the sole surviving texts of a movement named for its supposed founder, Pyrrho of Elis (ca. 360-275 BC). The Pyrrhonists held that human beings should suspend judgment on any question to which there was no clear answer, including the question whether anything can be known at all . . . For the Pyrrhonist, this suspension of judgment is meant to lead to a psychological stance of ataraxia, freedom from anxiety . . . Sextus’s writings were almost unknown in the Middle Ages, but Greek manuscript versions entered Italy in the fifteenth century, and a Latin edition of his Hypotyposes was published in 1562, followed by a Latin edition of all his works in 1569.

Eleven years later, the French thinker Michel de Montaigne (1533-92) published the first two books of his Essays, which were to have a major impact on religion and natural philosophy. Montaigne . . . looked out on his world and despaired. He had experienced the horror of the French civil wars, which broke out in 1562, at close range in his native Bordeaux; he also reacted negatively to the witch-craze: “It is,” he said, “taking one’s conjectures rather seriously to roast someone alive for them.” And he had read the [ancient] skeptics . . . The combination of tragic events and philosophical reading left Montaigne reeling. Nothing in this thought or experience, he felt, could be taken as immutably certain. Laws and customs are diverse and contradictory and vary with place and time. The religious wars showed that what is taken for divine truth one year may be condemned as execrable heresy the next. He said further, “What am I to make of a virtue that . . . becomes a crime on the other side of the river?”

In Montaigne’s view, the human faculties—reason, the senses, and passions—are all equally unreliable avenues to knowledge and truth. Reason “is like a tool” that can be adapted to support any clever argument or theory . . . The senses, like reason, are totally untrustworthy. First, how do we know that we have them at all? If we do not, there is no way of telling what we are missing. How, for example, can a blind man know what sight teaches? Second, we find that even the ones we do have can often be misleading under normal conditions and, even more so, when affected by the passions or poor health. Finally, Montaigne makes an argument that will be basic to the Scientific Revolution. A sense impression and the outside object that produces it are two quite different things. “So whoever judges from appearances judges from something quite different from the object itself”. The only things we have direct knowledge of are our sensations, and not the world they seem to represent . . . Here is our predicament. Our natural faculties yield nothing but uncertainty, but our arrogance mistakes for knowledge the misinformation we are fed by our senses and reason . . .

Pierre Charron, in Of Wisdom (1601), adopted Montaigne’s skepticism and took it in some striking new directions. Montaigne’s motto was “Que sais-je?” (“What do I know?”) But Charron said: “Je ne sais.” (“I do not know.”) He was even more emphatic that his master that human beings can know nothing with certainty. He followed Montaigne’s arguments to back up the point and extended one, the argument from cultural relativism, much further than Montaigne was willing to take it . . . For Charron, religions are especially important pieces of this baggage of custom, because they have such great authority among the common people. Christianity, like every other creed, is relative to its culture . . . for him, unlike Montaigne, all religions come close to being nothing more than human inventions, cultural artifacts, “maintained by human means and preserved by human hands.” . . . .

[The] greatest natural philosophers of seventeenth-century France would develop their views in response to the skepticism of Montaigne and Charron. [33-39]

René Descartes (1596-1650) . . . tried to establish new foundations for nothing less than all knowledge, both natural and moral. At La Flèche, one of the foremost Jesuit schools in France, he received a grounding in the traditional Scholastic curriculum, including Aristotelian science, which he later rejected . . .the only subject he singled out for praise from his previous education [was mathematics]. True to that conviction, Descartes went on to invent analytical geometry . . .

[Marin] Mersenne and [Pierre] Gassendi had argued that absolute certainty in the sciences is beyond the capacity of the human mind and that the best we can hope for from the sciences is probable certainty. But Descartes disagreed and set out to answer the skeptics by discovering the grounds for establishing necessary truth, conquering doubt, and building a new system to replace the false system of Aristotle. In this project, he proceeded by four stages, as laid out in his Discourse on the Method of Properly Conducting One’s Reason and of Seeking the Truth in the Sciences (1637).

The first step was to divest himself of all the erroneous opinions he had acquired as a result of his prior education . . . The second stage of Descartes’s argument extends the first into new territory. Not only does he reject what he has been taught, but he proceeds along a course of systematic doubt—distrusting both his reasoning and the testimony of his senses, and even wondering whether he is awake or asleep. If asleep, he says, he might just be dreaming. But he is quick to recover from his deep uncertainty when he finds that, no matter how much he doubts, he cannot doubt that he is doubting and arrives at his first fundamental truth: “I think; therefore, I am”. He exists and is essentially a thing that thinks, and this discovery leads him to the third stage in his quest for absolute certainty.

Third, as a thinking thing, he has innumerable thoughts, which may or may not have any truth, but Descartes has one more thought that carries its own conviction. He doubts and thereby recognizes his imperfection and, in that recognition, acknowledges the idea of perfection, which could only have been put into him by a perfect being. Hence God exists. We are now ready for step four. The existence of such a being guarantees that we can have true knowledge of a real world. A perfect God does not play tricks, and so we are not dreaming. The payoff is enormous. To the extent that we have “clear and distinct” ideas about the physical world, we can know nature, not through mere appearances, as Mersenne and Gassendi held, but for what it really is.

What are these clear and distinct ideas, these real truths, that Descartes said we can have? First, each of us knows ourself as a thinking thing. Second, we can also know objects outside our minds, including, first of all, our own bodies. God guarantees that this physical world is real and not illusory. But genuine knowledge of it does not come from the senses, because Descartes, like other contemporary philosophers, held that sensation is not an accurate representation of the outside world but only the product of a subjective encounter with it. Sensation yields a notoriously fallible account of the world. For true knowledge, Descartes relied, first of all, on mathematics, geometry in particular. We can know external objects clearly and distinctly to the extent that we can conceive of them as extended things reducible to their geometrical essences. This is the best knowledge—intuitive, innate, and purely intellectual. . . .Thus, Descartes, like Galileo, made a distinction between primary and secondary qualities of things. The primary qualities are their mathematically measurable characteristics—shape, size, position, and motion; the secondary qualities—for example, light, color, and texture—come to us through the unreliable senses and so cannot be trusted.

But, for Descartes, there was a second powerful source for true knowledge: metaphysics . . . he produced a philosophical physics deduced from first principles. His aim was nothing less than to replace the philosophical system of Aristotle and the Scholastics with his own new, and better system, which would explain all the processes of nature, or at least provide the correct foundation for explaining them. The resulting Cartesian system was to have enormous influence on philosophy and science throughout the remainder of the seventeenth century . . .

First of all, it is a mechanical philosophy. Everything in the physical world is made up of matter in motion and is put in motion initially by God. [77-79]

1) In your own words, explain the historical context & significance of Descartes’s famous phrase: “I think; therefore, I am.” 2) In your own words, explain how Descartes’s response to modern skepticism is accurately described as “deductive rationalism” [this term was discussed in class].