Rules for the Direction of the Mind

In 1619, René Descartes began work on an unfinished treatise regarding the proper method for scientific and philosophical thinking entitled Regulae ad directionem ingenii, or Rules for the Direction of the Mind. This work outlined the basis for his later work on complex problems of mathematics, science, and philosophy. 36 rules were planned in total, although only 21 were actually written.

The first 12 rules deal with his proposed scientific methodology in general. Analysts consider them to be early versions of principles that he expanded upon in his later writings.

Rules

Rule I

The aim of our studies must be the direction of our mind so that it may form solid and true judgements on whatever matters arise.

Rule II

We must occupy ourselves only with those objects that our intellectual powers appear competent to know certainly and indubitably.

Rule III

As regards any subject we propose to investigate, we must inquire not what other people have thought, or what we ourselves conjecture, but what we can clearly and manifestly perceive by intuition or deduce with certainty. For there is no other way of acquiring knowledge.

Rule IV

There is need of a method for finding out the truth.

Rule V

Method consists entirely in the order and disposition of the objects towards which our mental vision must be directed if we would find out any truth. We shall comply with it exactly if we reduce involved and obscure propositions step by step to those that are simpler, and then starting with the intuitive apprehension of all those that are absolutely simple, attempt to ascend to the knowledge of all others by precisely similar steps.

Rule VI

In order to separate out what is quite simple from what is complex, and to arrange these matters methodically, we ought, in the case of every series in which we have deduced certain facts the one from the other, to notice which fact is simple, and to mark the interval, greater, less, or equal, which separates all the others from this.

Rule VII

If we wish our science to be complete, those matters which promote the end we have in view must one and all be scrutinized by a movement of thought which is continuous and nowhere interrupted; they must also be included in an enumeration which is both adequate and methodical.

Rule VIII

If in the matters to be examined we come to a step in the series of which our understanding is not sufficiently well able to have an intuitive cognition, we must stop short there. We must make no attempt to examine what follows; thus we shall spare ourselves superfluous labour.

Rule IX

We ought to give the whole of our attention to the most insignificant and most easily mastered facts, and remain a long time in contemplation of them until we are accustomed to behold the truth clearly and distinctly.

Rule X

In order that it may acquire sagacity the mind should be exercised in pursuing just those inquiries of which the solution has already been found by others; and it ought to traverse in a systematic way even the most trifling of men's inventions though those ought to be preferred in which order is explained or implied.

Rule XI

If, after we have recognised intuitively a number of simple truths, we wish to draw any inference from them, it is useful to run them over in a continuous and uninterrupted act of thought, to reflect upon their relations to one another, and to grasp together distinctly a number of these propositions so far as is possible at the same time. For this is a way of making our knowledge much more certain, and of greatly increasing the -power of the mind.

Rule XII

Finally we ought to employ all the aids of understanding, imagination, sense and memory, first for the purpose of having a distinct intuition of simple propositions; partly also in order to compare the propositions to be proved with those we know already, so that we may be abk to recognize their truth; partly also in order to discover the truths, which should be compared with each other so that nothing may be left lacking on which human industry may exercise itself.

Rule XIII

Once a "question" is perfectly understood, we must, free it of every conception superfluous to its meaning, state it in its simplest terms, and, having recourse to an enumeration, split it up into the various sections beyond which analysis cannot go in minuteness.

Rule XIV

The same rule is to be applied also to the real extension of bodies. It must be set before the imagination by means of mere figures, for this is the best way to make it clear to the understanding.

Rule XV

It is likewise very often helpful to draw these figures and display them to the external senses, in order thus to facilitate the continued fixation of our attention.

Rule XVI

When we come across matters which do not require our present attention, it is better, even though they are necessary to our conclusion, to represent them by highly abbreviated symbols, rather than by complete figures. This guards against error due to defect of memory on the one hand, and, on the other, prevents that distraction of thought which an effort to keep those matters in mind while attending to other inferences would cause.

Rule XVII

When a problem is proposed for discussion we should run it over, taking a direct course, and for this reason neglecting the fact that some of its terms are known, others unknown. To fottow the true connection, when presenting to mind the dependence of separate items on one another, will also aid us to do this.

Rule XVIII

To this end only four operations are required, addition, subtraction, multiplication and division. Of these the two latter are often to be dispensed with here, both in order to avoid any unforeseen complication, and because it will be easier to deal with them at a later stage.

Rule XIX

Employing this method of reasoning we have to find out as many magnitudes as we have unknown terms, treated as though they were known, for the purpose of handling the problem in the direct way; and these must be expressed in the two different ways. For this will give us as many equations as there are unknowns.

Rule XX

Having got our equations, we must proceed to carry out such operations as we have neglected, taking care never to multiply where we can divide.

Rule XXI

If there are several equations of this kind, we should reduce them all to a single one, viz. that the terms of which do not occupy so many places in the series of magnitudes that are in continued proportion. The terms of the equation should then be themselves arranged in the order which this series follows.

References

• Douglas Burnham and James Fieser. "René Descartes (1596-1650)". Internet Encyclopaedia of Philosophy. http://www.utm.edu/research/iep/d/descarte.htm. Retrieved August 9, 2005. 

Republications

• Descartes, R. (June 2000). Rules for the Direction of the Mind. Bobbs-Merrill Co. ISBN 0-672-60334-9.