Rules for the Direction of the Mind

Overview

The Rules is eighty pages, it was never finished, and Descartes never published it. He worked on it in stages between about 1619 and 1628, planned thirty-six rules in three groups of twelve, wrote eighteen with commentary, gave the next three titles and no text, and abandoned the rest. It appeared in print in 1684, more than thirty years after he died.

That makes it an unusual thing to read: a major philosopher’s working draft, with the joins visible and the project incomplete. It also makes it the clearest statement of what Descartes thought he was doing before the metaphysics arrived. There is no evil demon here, no cogito, no proof of God. The problem is not whether we can know anything. The problem is that we know things badly, in a disorganised way, from the wrong sources, and that there ought to be a procedure.

Each rule is a short maxim followed by several pages of discussion, and the discussion is where the interest is. The style is confident, occasionally contemptuous, and much less careful than the published work.

Read it after the Discourse and before the Meditations, and you can watch a method turn into a philosophy.

The argument

Rules 1 to 3: what knowledge is. The first rule attacks the way learning was organised. People study a science the way a craftsman learns a trade, as if each required a different aptitude, and they choose subjects for their usefulness. Descartes says this misunderstands what is happening: the sciences are all one thing, human reason, which is no more altered by its objects than sunlight is altered by what it falls on. So the aim of study is not to accumulate results in a field but to improve the instrument.

Rule 2 is severe. Attend only to objects about which certain and indubitable knowledge is available. That excludes most of what passed for learning, and Descartes is explicit that on this standard arithmetic and geometry are the only disciplines so far in good order, precisely because they deal in objects so pure and simple that there is nothing to get wrong.

Rule 3 names the two operations that produce knowledge. Intuition is the undoubting conception of a clear and attentive mind, which arrives all at once, and by which one sees that a triangle is bounded by three lines or that one is thinking. Deduction is inference from things known with certainty, and it differs from intuition only in having a movement and a sequence, and therefore in depending on memory. Syllogism, probability, and what other people have believed are all set aside.

Rules 4 to 8: the method. Rule 4 defines method as rules so certain and easy that following them exactly makes error impossible and spares effort. Inside its discussion comes the passage about mathesis universalis: Descartes notices that arithmetic, geometry, astronomy, music and optics all study order and measure, and proposes that there should be a general science of order and measure as such, not tied to any particular material.

Rules 5 and 6 give the core procedure: reduce obscure and complicated propositions step by step to simpler ones, then climb back up the same ladder. To do that you sort the things involved into the absolute, which are simple and independent, and the relative, which depend on others, and you arrange them in a series.

Rule 7 requires enumeration, a complete and orderly sweep so that nothing is omitted and the whole chain can be run through fast enough to be held as a single view. Rule 8 is about knowing when to stop, and contains the striking argument that anyone seriously investigating the truth must at some point examine the mind itself, since everything else depends on it.

Rules 9 to 12: the faculties. Rule 12 is the longest in the book and it is the philosophical centre. Descartes sets out how knowledge actually happens: external sense receives figures, the common sense transfers them, imagination holds them, memory stores them, and the understanding works on them. He introduces simple natures, the elements into which any problem finally resolves, some intellectual, some material, some common to both, and argues that error never lies in these but in how we combine them. This is a theory of mind built for a method rather than for metaphysics, and it gives the imagination a serious cognitive role that the later Descartes withdraws.

Rules 13 to 21: applying it. The remainder turns to what he calls perfectly understood problems, in which everything needed is given and the task is to find the relation. Here the method becomes concretely algebraic: state what is known and unknown, find the way they are connected, reduce to an equation, and solve. Rules 19 to 21 have titles and no commentary, and the manuscript stops.

How to read it

Read Rules 1 to 8 and Rule 12. That is the argument, and it is perhaps thirty pages.

Then read the four rules of method in Part II of the Discourse on Method and compare. The Discourse is famous and compressed to the point of blandness; the Rules show what each of those sentences was supposed to carry.

Notice what is missing. There is no scepticism to be defeated, no God guaranteeing clear ideas, no mind-body problem. Descartes here simply assumes the mind can see truths clearly, and the whole later apparatus of the Meditations exists to license what this book takes for granted.

Ask why he stopped. The usual answers are that the later rules required a mathematics he had not finished, that the imagination-centred account of thinking in Rule 12 was one he came to reject, or that he realised the method needed a metaphysical foundation before it could be defended. The text gives some support to each.

Treat the confidence as evidence. This is a young man who believes discovery can be reduced to a procedure that anyone can follow. Whether any of the later work shows him still believing it is a good question to carry through the rest of Descartes.

Questions it raises

• Can discovery really be made a procedure? Descartes promises rules that make error impossible. Has anyone ever found such rules for anything?
• Rule 2 says attend only to what can be known with certainty. What happens to medicine, history and politics under that restriction?
• Intuition is described as an undoubting conception of a clear and attentive mind. How would you tell a genuine intuition from a confident mistake?
• If all the sciences are one human reason applied to different material, why do they need different training?
• Mathesis universalis proposes a general science of order and measure. What would that even look like, and did anything become it?
• Descartes abandoned the book. What in it do you think he no longer believed by the time of the Meditations?