Book V.
ON FALLACIES.
- "Errare non modo affirmando et negando, sed etiam sentiendo, et in tacitâ hominum cogitatione contingit."--HOBBES, Computatio sive Logica, chap. v.
- "Il leur semble qu'il n'y a qu'à douter par fantaisie, et qu'il n'y a qu'à dire en général que notre nature est infirme; que notre esprit est plein d'aveuglement: qu'il faut avoir un grand soin de se défaire de ses préjugés, et autres choses semblables. Ils pensent que cela suffit pour ne plus se laisser séduire à ses sens, et pour ne plus se tromper du tout. Il ne suffit pas de dire que l'esprit est faible, il faut lui faire sentir ses faiblesses. Ce n'est pas assez de dire qu'il est sujet à l'erreur, il faut lui découvrir en quoi consistent ses erreurs."--MALEBRANCHE, Recherche de la Vérité.
Chapter I.
Of Fallacies In General.
§ 1. It is a maxim of the school-men, that "contrariorum eadem est
scientia:" we never really know what a thing is, unless we are also able
to give a sufficient account of its opposite. Conformably to this maxim,
one considerable section, in most treatises on Logic, is devoted to the
subject of Fallacies; and the practice is too well worthy of observance,
to allow of our departing from it. The philosophy of reasoning, to be
complete, ought to comprise the theory of bad as well as of good
reasoning.
We have endeavored to ascertain the principles by which the sufficiency of any proof can be tested, and by which the nature and amount of evidence needful to prove any given conclusion can be determined beforehand. If these principles were adhered to, then although the number and value of the truths ascertained would be limited by the opportunities, or by the industry, ingenuity, and patience, of the individual inquirer, at least error would not be embraced instead of truth. But the general consent of mankind, founded on their experience, vouches for their being far indeed from even this negative kind of perfection in the employment of their reasoning powers.
In the conduct of life--in the practical business of mankind--wrong inferences, incorrect interpretations of experience, unless after much culture of the thinking faculty, are absolutely inevitable; and with most people, after the highest degree of culture they ever attain, such erroneous inferences, producing corresponding errors in conduct, are lamentably frequent. Even in the speculations to which eminent intellects have systematically devoted themselves, and in reference to which the collective mind of the scientific world is always at hand to aid the efforts and correct the aberrations of individuals, it is only from the more perfect sciences, from those of which the subject-matter is the least complicated, that opinions not resting on a correct induction have at length, generally speaking, been expelled. In the
