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


The Rules:

Rule I.— The end of studies should be the discipline of the mind, such as shall enable it to pass true and solid judgments upon any subject which may present itself.

Rule II.— We should occupy ourselves only with those subjects in reference to which the mind is capable of acquiring certain and indubitable knowledge.

Rule III.—In regard to the subject of our studies we should seek, not what others may have thought about it, not what we ourselves may suspect to be true, but what we can see clearly and with evidence, or deduce with certainty.

Rule IV.—Necessity of method in the search for truth.

Rule V.—The whole method consists in the order and arrangement of the subjects upon which the mind is to exert itself with the view to attain truth.

Rule VI.— To distinguish the simpler things from those which are more complex, it is necessary, in every series of objects, or in every case where we have deduced some truths from others, to take note of the simplest of all, and to observe how all the rest stand removed from this, whether more or less or equally.

Rule VII.—In order to make knowledge complete, it is necessary the mind should run over, in a movement uninterrupted and orderly, all matters pertaining to the end in view, and then sum them up in a methodical and sufficient enumeration.

Rule VIII.—If in the course of our investigations anything presents itself which the mind cannot perfectly comprehend, we must stop at that point and not examine what comes next, but spare ourselves fruitless labor.

Rule IX.— It is necessary to direct the whole energy of the mind upon things which are easiest and least important, and to hold it there for a long time until the habit is acquired of seeing truth clearly and distinctly.

Rule X.—In order that the mind may acquire facility, it must be exercised in finding out things which others have already discovered, and in practicing in a methodical way even the commonest arts, especially those which exhibit order or require it.

Rule XI.— When by intuition we have assured ourselves of the truth of certain simple propositions, if we are to proceed to draw conclusions therefrom, it is of no use to go on without arresting for a moment the progress of our thought, in order to reflect upon the mutual relations of these truths, and to bring as many as possible of these relations before the mind in one view: by this means we give to our knowledge more certainty and to our thought greater breadth.

Rule XII.—Finally, all the resources of intellect, of imagination, of the senses, of memory, must be employed, in order to have a distinct intuition of simple propositions, to compare suitably what is sought with what is known, and to find out the things which are thus to be compared together; in a word, no one of the means of knowledge with which the human mind is provided, is to be neglected.