§ 2. Of affirmative and negative propofitions, 136 3. Of the oppofition and converfion of pro- 4. Of pure and moral propofitions, 2. Prejudices arifing from words, 3. Prejudices arifing from ourselves, 4. Prejudices arifing from other perfons, CHAP. IV. General directions to affift us in judg- CHAP. V. Special rules to direct us in judging of The Third Part, namely, Of Reasoning CHAP. I. Of the nature of a fyllogifm, and of the parts of which it is compofed, CHAP. II. Of the various kinds of fyllogifms, with particular rules relating to them, § Of univerfal and particular fyllogifms, 7. Of the middle terms, of common places or topics, and invention of arguments, 8. Of feveral kinds of arguments and de- CHAP. III. The doctrine of Syllogifms, § 1. Of feveral kinds of sophisms and their so- 2. Two general tefts of true fyllogifms, and 257 The Fourth Part, namely, Of Method. CHAP. I. The nature and kinds of method, viz. INTRODUCTION AND GENERAL SCHEME. OGIC is the art of ufing REASON * well in our inquiries after truth, and the communication of it to others. REASON is the glory of human nature, and one of the chief eminencies whereby we are raised above our fellow-creatures, the brutes, in this lower world. Reafon, as to the power and principle of it, is the common gift of God to all men, though all are not favoured with it by nature in an equal degree; but the acquired improvements of it in different men, make a much greater diftinction between them than nature had made. I could even venture to say, that the improvement of reafon hath raised the learned and the prudent in the European world, almoft as much above the Hottentots, and other favages of Africa, as thofe favages are by nature fuperior to the birds, the beafts, and the fishes. Now the defign of Logic is to teach us the right use of our reason, or intellectual powers, and the improvement of them in ourselves and others? This is not only neceffary in order to attain any competent knowledge in the fciences, or the affairs of learning but to govern both the greater and the meaner actions of life. It is the cultivation of our reafon by which we are better enabled to diftinguifh good from evil, as well *The word Reafon in this place is not confined to the mere faculty of reafoning, or inferring one thing from another, but includes all the intellectual powers of man. B as truth from falsehood; and both these are matters of the highest importance, whether we regard this life, or the life to come. The purfuit and acquifition of truth is of infinite concernment to mankind. Hereby we become acquainted with the name of things both in heaven and earth, and their various relations to each other. It is by this means we discover our duty to God and our fellow-creatures; by this we arrive at the knowledge of natural religion, and learn to confirm our faith in divine revelation, as well as to understand what is revealed. Our wifdom, prudence, and piety, our present conduct and our future hope, are all influenced by the ufe of our rational powers in the fearch after truth. There are feveral things that make it very neceffary that our reafon fhould have fome affiftance in the exercife or use of it. The first is, the depth and difficulty of many truths and the weakness of our reafon to fee far into things at once, and penetrate to the bottom of them. It was a faying among the ancients, Veritas in puteo, truth lies in a well; and, to carry on this metaphor, we may very justly fay, that logic does, as it were, fupply us with fteps whereby we may go down to reach the water or it frames the links of a chain, whereby we may draw the water up from the bottom. Thus, by the means of many reafonings well connected together, philofophers in our age have drawn a thousand truths out of the depths of darkness, which our fathers were utterly unacquainted with. Another thing that makes it neceffary for our reafon to have fome affiftance given it, is the difguife and falfe colours in which many things appear to us in this prefent imperfect ftate. There are a thoufand things which are not in reality what they appear to be, and that both in the natural and moral world; fo that the fun appears to be flat as a plate of filver, and to be lefs than, twelve inches in diameter; the moon appears to be as big as the fun; and the rainbow appears to be a large fubftantial arch in the fky; all which are in reality grofs falfehoods, So knavery puts on the face of justice; hypocrify and fuperftition wear the vizard of piety, deceit and evil are often cloathed in the fhapes and appearances of truth and goodness. Now logic helps us to ftrip off the outward difguife of things, and to behold them and judge of them in their own nature. There is yet a farther proof of our intellectual or rational powers needing fome afliftance, and that is, because they are fo frail and fallible in the present state: We are impofed upon at home as well as abroad; we are deceived by our fenfes, by our imaginations, by our pallions and appetites; by the authority of men, by education and custom, &c; and we are led into frequent errors, by judging according to thefe falfe and flattering principles, rather than according to the nature of things. Something of this frailty is owing to our very conftitution, man being compounded of flesh and fpirit; fomething of it arifes from our infant ftate, and our growing up by fmall degrees to manhood; fo that we form a thoufand judgments before our reason is mature. But there is ftill more of it owing to our original defection from God, and the foolish and evil difpofitions that are found in fallen man; fo that one great part of the defign of logic is to guard us against the delufive influences of our meaner powers, to cure the mistakes of immature judgment, and to raife us in fome measure from the ruins of our fall. It is evident enough from all thefe things, that our reafon needs the affiftance of art in our inquiries after truth or duty and without fome fkill and diligence in forming our judgment aright, we fhall be led into frequent mistakes, both in matters of science, and in matters of practice; and fome of these mistakes may prove fatal too. The art of logic, even as it affifts us to gain the knowledge of the fciences, leads us on towards virtue and happiness; for all our fpeculative acquaintance with things fhould be made fubfervient to our better conduct in the civil and the religious life. This is infinitely more valuable than all fpeculations, and a wife man will ufe them chiefly for this better purpose. All the good judgment and prudence that any man exerts in his common concerns of life, without the advantage of learning, is called natural logic; and it is |