It is then for each of us a duty to instruct himself, but it is evident that this duty must be regarded as a broad duty—that is to say, that its application cannot be determined by precise formulas. No man is obliged by the moral law to be what is called a scholar; no one is obliged to learn astronomy or transcendental mathematics, still less metaphysics. But it can be said that it is a duty for each of us: 1. To learn as well as possible the principles of the art he will have to cultivate: for instance, the magistrate the principles of jurisprudence; the physician the principles of medicine; the artisan the principles of mechanics. In this respect young students, we must confess, have far too easy a conscience. They do not realize the responsibility they incur by their negligence and laziness. 2. It is a duty for all men, according to the means they can dispose of, to instruct themselves concerning their duties. 3. It is also a duty for each to go, as far as he can, beyond the strictly necessary in matters of education, and in proportion to the means he has at his disposal. It is then a duty to neglect no occasion of improving one’s self.
149. Good sense.—Between science and prudence, between theoretical intelligence and practical intelligence, Aristotle places the critical faculty—in other terms, judgment, good sense, discernment. This faculty is distinguished from science in that it is only applied to things where doubt and deliberation come in; it treats then of the same objects as prudence; but it is distinguished from the latter in that prudence is practical and prescribes what should be done or not be done; good sense, on the contrary, is purely critical: it is limited to mere judging. It is, then, in some respects disinterested and does not induce to action; it is the art of appreciating things, men, and events. Good judgment may be found among men lacking practical prudence: one sees often very well the faults of others without seeing one’s own; or, again, one may be aware of one’s own faults and not be able to correct them. However, it is not to be denied that good sense or good judgment is a useful auxiliary to prudence; it is already in itself an estimable quality, and is far from being as well distributed among men as Descartes claims.[117] On the contrary, according to Nicole:
“Common sense is not so common a quality as one thinks.... Nothing is more rare than this exactness of judgment. Everywhere we meet false minds who have scarcely any discernment of what is true; who take everything the wrong way; who accept the worst kind of reasonings, and wish to make others accept them also; who allow themselves to be carried away by the least appearances of things; who are always excessive in their views and run into extremes; minds who either have no grasp to hold on to the truths they have acquired, because they have become attached to them through chance rather than solid knowledge; or who, on the contrary, persist in their ideas with such stubbornness that they listen to nothing that could undeceive them; who judge boldly of things neither they nor any one else, perhaps, ever understood; who make no difference between talking to the purpose and talking nonsense, and are guided in their judgment by mere trifles.... So that there are no absurdities, however incredible, that do not find approving adherents. Whoever intends duping people is sure to find people glad to be duped, and the most ridiculous nonsense is sure to find minds suited for it.”
Here, the rules of morality are confounded with those of logic. It is the latter that teaches us how to avoid error, if not in science (which is the object of speculative logic), at least in life. The development of these rules will be found in the Recherche de la vérité of Malebranche. The Logique de Port Royal will furnish us a résumé of them which will suffice here:
150. Illusions coming from ourselves.—1. A first cause of illusion in the judgments we pass upon things, is to take our interest for a motive of belief: “I am of such or such a country, ergo, I must believe that such or such a saint has preached the Gospel there; I belong to such or such a class, ergo, I believe that such or such a privilege is a just one.”
2. Our affections are another cause of illusion: “I love him, ergo, he is the cleverest man in the world; I hate him, ergo, he is nobody.” This is what may be called the sophistry of the heart.
3. Illusions of self-love. There are some who decide about everything by the general and very convenient principle, that they must be in the right. They listen but little to the reasons of others; they wish to carry everything before them by main authority, and treat all those who are not of their opinion as indifferent thinkers. Some even, without suspecting it, go so far as to say to themselves: “If it were so, I should not be the clever man I am: or, I am a clever man; ergo, it is not so.”
4. Reciprocal reproaches which people may make to each other with the same right: for example, you are a caviler, you are selfish, blind, dishonest, etc. Whence this equitable and judicious rule of Saint Augustine: “Let us avoid in discussions mutual reproaching; reproaches which, though they may not be true at that moment, may justly be made by both parties.”
5. A spirit of contradiction and dispute, so admirably depicted by Montaigne:
“We only learn to dispute that we may contradict, and every one contradicting and being contradicted, it falls out that the fruit of disputation is to lose and nullify the truth.... One flies to the east, the other to the west; they lose the principal, and wander in the crowd of incidents; after an hour of tempest, they know not what they seek; one is low, the other high, and a third wide; one catches at a word and a simile; another is no longer sensible of what is said in opposition to him, being entirely absorbed in his own notions, engaged in following his own course, and not thinking of answering you; another, finding himself weak, fears all, refuses all, and, at the very beginning, confounds the subjects, or, in the very height of the dispute, stops short, and grows silent; by a peevish ignorance affecting a proud contempt, or an unseasonable modest desire to shun debate....”