Rules for the Direction of the Mind

Summary

The Regulae ad directionem ingenii is the young Descartes's attempt to write down the method he believed he had found in mathematics and to show that it could govern every inquiry. He planned thirty-six rules in three groups of twelve: rules for simple propositions, for problems that are perfectly understood, and for problems that are imperfectly understood. He finished only twenty-one, and the last three are bare statements without explanation. The manuscript lay among his papers when he died in Stockholm in 1650; a Dutch translation appeared in 1684 and the Latin was first printed in Amsterdam in 1701. Rule I sets the aim of study: to direct the mind so that it forms solid and true judgments about whatever comes before it. Descartes argues that the sciences are not separate habits, like the skills of different crafts, but one human wisdom that stays the same however many subjects it lights, as the sun's light is not altered by the variety of things it shines on. Rule II restricts study to objects of which certain knowledge is possible and sets aside merely probable opinion, which is why arithmetic and geometry are the model. Rule III names the only two sure acts of the mind: intuition, the undoubting grasp of a pure and attentive mind, and deduction, the necessary inference from things intuited. Rule IV insists that method is necessary and speaks of a universal mathematics concerned with order and measure in any subject. Rules V to VII describe the method itself: reduce complex and obscure propositions step by step to simpler ones, arrange things in series from the absolute to the relative, and survey every link by a complete enumeration. Rules VIII to XI discuss the limits of knowledge, the habit of dwelling on the simplest things, the training of sagacity on ordered crafts, and running through a chain of inferences until it can be seen almost at once. Rule XII discusses the faculties of understanding, imagination, sense and memory and the 'simple natures' from which all knowledge is composed. The second half applies these principles to problems of magnitude: strip a question to its essentials, represent magnitudes as lines and figures, draw them, use brief symbols to relieve the memory, and set up as many equations as unknowns. That programme reappears, worked out, in the Geometry of 1637. The Rules show Descartes's method before the radical doubt of the Meditations, and they let students ask whether rules of right thinking can be written down at all.

Top Lessons

• One wisdom, many subjects

  Rule I denies that each science needs its own separate mind, as each craft needs its own trained hand. Wisdom is one, like sunlight on many objects, so the student should seek to strengthen the natural light of reason rather than collect specialisms. The claim echoes and also unsettles the classical idea of an ordered curriculum.

• Intuition and deduction as the only roads

  Rule III allows two acts of mind to yield knowledge: intuition, a conception so clear and attentive that no doubt remains, and deduction, which joins intuited steps by necessity. Reading the ancients is useful, Descartes says, but agreeing with their conjectures is not knowing. The rule sets the standard that the Meditations later test against radical doubt.

• Break the hard problem into easy steps

  Rules V to VII say that the whole method is order: lead complex propositions back to the simplest, then climb back up, checking every link by enumeration. Rule X adds that sagacity is trained on simple ordered crafts and puzzles before difficult questions. Students can apply this directly to a hard proof or a long essay.

• Pictures and symbols as aids to a finite mind

  In Rules XIV to XVI Descartes admits that the understanding needs help: magnitudes are best pictured as lines and rectangles, and what need not be held in view should be written in brief signs so that memory is not overloaded. The method is designed for a limited human mind, not an angelic one, and it leads straight to the algebraic notation of the Geometry.

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Medical Lens

The Rules are a treatise on method, not medicine, but Rule XII contains Descartes's earliest written sketch of the physiology of sensation and imagination: the external senses receive figures passively, they are conveyed to a common sense, and imagination or fantasy is described as a real part of the body connected with the nerves. This anticipates the mechanical psychology of the Treatise on Man and the Passions of the Soul. The repeated concern with the weakness of memory in long deductions (Rules VII, XI and XVI) is a cognitive rather than clinical theme.

• Rule XII

  Sketch of how sensation works: the senses are affected as wax by a seal, figures pass to the common sense and are impressed on the fantasy or imagination, which Descartes treats as a bodily organ able to move the nerves.

• Rules VII, XI and XVI

  Descartes treats memory as the weak point of long chains of reasoning and prescribes rapid repeated surveys and written symbols to relieve it.