Philosophy: A Very Short Introduction

On top of which the new scientists want to replace explanations couched in terms of natures and goals with talk of the particles of which things are composed, and of mechanical causation governed by mathematical laws.
All this represented catastrophic intellectual change on several levels at once. It is often called the Scientific Revolution, a name which captures its magnitude, but wrongly suggests that it happened quickly. No wonder that it was accompanied by a rise of scepticism. For if the best of received wisdom, with two thousand years of triumphant history, was now seen to be failing, a natural reaction was to despair of human knowledge altogether and call off the hunt.
René Descartes (1596–1650) viewed Aristotelianism as a time-hallowed system of errors. So did the sceptics, but unlike them he also took it to be an obstacle—an obstacle to human knowledge of nature, like scepticism itself. So he conceived an ambitious plan. (Had he known just how ambitious he might have stopped in his tracks there and then—so we should be glad that he didn’t.) By going back to a point at which no doubt was even possible and then rebuilding human knowledge by unmistakable steps he would fight his way clear of scepticism, and presumably of Aristotelianism as well, since he had no expectation that his reconstruction would lead back in that old, worn, faltering direction. Then he would illustrate the value of this heroic Great Escape of the human intellect by demonstrable progress in the sciences: optics, physics, physiology, and meteorology were all topics that he wrote about.
The Discourse on the Method of rightly using one’s Reason (1637) is not Descartes’s most famous work—that title surely goes to his Meditations (1641). But it has the advantage of giving the reader, in very brief compass, a taste of most of Descartes’s thought, including very importantly an autobiographical account of the circumstances and motivation from which his whole project arose.
So set aside a couple of hours—easily enough—and begin by sympathizing with Descartes’s frustration when formal education left him feeling that ‘I had gained nothing . . . but increasing recognition of my ignorance’ and that there was ‘no such knowledge in the world as I had previously been led to hope for’. Admittedly, there is value in some of what he has been taught, and he gives a sentence each to the advantages of languages, history, mathematics, oratory, and poetry—though the latter two are ‘more gifts of the mind than fruits of study’. As for philosophy, its chief ‘advantage’ is that it enables us to ‘speak plausibly about any subject and win the admiration of the less learned’—so much for scholastic Aristotelianism. So the minute he is old enough he chucks it all in and goes travelling, joining in the wars which were boiling away in Europe at this time. Perhaps men of action will have more truth to offer than the scholars; after all, their misjudgements really do rebound on them, whereas those of the scholars have no practical consequences and can be false with impunity.
One thing he learns on his travels is how much customs differ from place to place, people to people—as he pointedly says, there is as much variety as in the opinions of the philosophers—so he had better not rely on anything he has learnt only through ‘custom and example’. At this stage many people (and nowadays even more than then) might slip into a forlorn scepticism or a lazy relativism. But not this one. Descartes’s reaction is that if he is to avoid living under the misguidance of false opinions then once in his life he should dismantle his entire belief-system and construct it anew. Which he intends to try—and on his own what’s more.
One has to be amazed at the audacity of this unflinchingly positive response to the crisis that Descartes, doubtless along with many less articulate or less self-confident contemporaries, was experiencing. If, that is, we believe that he really meant it—but I know no good reason to think that he didn’t. In Part 2 of the Discourse we see him striving to reassure any readers who may take him for a social, political, or theological reformer: ‘No threat to any public institution, it’s only my own beliefs that I’m going to overhaul.’ (Prudent, and a nice try, but not altogether convincing, is it? As if he weren’t going to recommend his renovated belief-system to anyone else!) Then in Part 3 he takes steps to ensure that his life can keep ticking over while his beliefs are suspended, for ‘before starting to rebuild your house you must provide yourself with somewhere to live while building is in progress’. So he will simply go along, non-committally, with the most sensible and moderate views and behaviour he finds around him. It is a modified version of what he would have found in Sextus Empiricus’ report of the recommendations of the ancient sceptics—who faced the same problem permanently, since they had no intention of rebuilding.
How is demolition to proceed, and where will Descartes find his foundations? At the start of Part 4 he suddenly feigns to go all shy: perhaps he should bypass this bit, as being ‘too metaphysical and uncommon for everyone’s taste’. But then he tells us anyway. What we get in Part 4 is a high-speed résumé of his best-known work, the Meditations on First Philosophy.
First, suspend any belief about which you can think of the slightest grounds for doubt. (Don’t bother about whether these grounds actually do make you feel doubtful—mostly they won’t, but that could just be a fact about you.) Since your senses have sometimes deceived you, consider the possibility that they might deceive you at any time, indeed that they might deceive you all the time—that they have no more status than a dream or a hallucination. But what about your belief that you are now thinking? Here doubt really does run dry, because doubting whether you are thinking is another case of thinking—the doubt defeats itself. And