its first principles are ascertained: after which, it advances regularly, and fecures the ground it has gained.

Although firft principles do not admit of direct proof, yet there must be certain marks and characters, by which those that are truly fuch may be distinguished from counterfeits. Thefe marks ought to be defcribed, and applied, to distinguish the genuine from the fpurious.

In the ancient philofophy, there is a redundance, rather than a defect, of first principles. Many things were affumed under that character without a just title: That nature abhors a vacuum; That bodies do not gravitate in their proper place; That the heavenly bodies undergo no change; That they move in perfect circles, and with an equable motion. Such principles as these were affumed in the Peripatetic philofophy, without proof, as if they were felf-evident.

Des Cartes, fenfible of this weaknefs in the ancient philofophy, and defirous to guard against it in his own fyftem, refolved to admit nothing until his affent was forced by irrefiftible evidence. The first thing that he found to be certain and e

vident

vident was, that he thought, and reafoned, and doubted. He found himself under a neceffity of believing the existence of those mental operations of which he was confcious and having thus found fure footing in this one principle of conscioufnefs, he rested fatisfied with it, hoping to be able to build the whole fabric of his knowledge upon it; like Archimedes, who wanted but one fixed point to move the whole earth. But the foundation was too narrow; and in his progress he unawares affumes many things lefs evident than those which he attempts to prove. Altho' he was not able to suspect the testimony of consciousnefs; yet he thought the testimony of fenfe, of memory, and of every other faculty, might be fufpected, and ought not to be received until proof was brought that they are not fallacious. Therefore he applies these faculties, whose character is yet in queftion, to prove, That there is an infinitely perfect Being, who made him, and who made his fenfes, his memory, his reafon, and all his faculties; That this Being is no deceiver, and there· fore could not give him faculties that are fallacious;

fallacious; and that on this account they deferve credit.

It is strange, that this philofopher, who found himself under a neceffity of yielding to the testimony of consciousness, did not find the fame neceffity of yielding to the testimony of his fenfes, his memory, and his understanding: and that while he was certain that he doubted, and reafoned, he was uncertain whether two and three made five, and whether he was dreaming or awake. It is more strange, that fo acute a reafoner fhould not perceive, that his whole train of reasoning to prove that his faculties were not fallacious, was mere fophiftry; for if his faculties were fallacious, they might deceive him in this train of reafoning; and fo the conclufion, That they were not fallacious, was only the teftimony of his faculties in their own favour, and might be a fallacy.

It is difficult to give any reason for distrusting our other faculties, that will hot reach consciousness itself. And he who distrusts the faculties of judging and reafoning which God hath given him, must even reft in his fcepticism, till he

come

come to a found mind, or until God give him new faculties to fit in judgement upon the old. If it be not a first principle, That our faculties are not fallacious, we must be abfolute fceptics: for this principle is incapable of proof; and if it is not certain, nothing else can be certain.

Since the time of Des Cartes, it has been fashionable with those who dealt in abstract philosophy, to employ their invention in finding philofophical arguments, either to prove thofe truths which ought to be received as firft principles, or to overturn them: and it is not easy to say, whether the authority of first principles is more hurt by the first of these attempts, or by the laft: for fuch principles can stand secure only upon their own bottom; and to place them upon any other foundation than that of their intrinfic evidence, is in effect to overturn them.

I have lately met with a very fenfible and judicious treatise, wrote by Father Buffier about fifty years ago, concerning first principles and the fource of human judgements, which, with great propriety, he prefixed to his treatise of logic. And

indeed I apprehend it is a fubject of fuch confequence, that if inquifitive men can be brought to the fame unanimity in the first principles of the other sciences, as in those of mathematics and natural philofophy, (and why should we despair of a general agreement in things that are felfevident?), this might be confidered as a third grand æra in the progress of human reafon.

END of the THIRD VOLUME.