and of science: We fhall not pretend to abridge those books; for Ariftotle's writings do not admit of abridgement: no man can fay what he says in fewer words; and he is not often guilty of repetition. We shall only give fome of his capital conclufions, omitting his long reasonings and nice distinctions, of which his genius was wonderfully productive.

All demonstration must be built upon principles already known; and these upon others of the fame kind; until we come at last to first principles, which neither can be demonstrated, nor need to be, being evident of themselves.

We cannot demonftrate things in a circle, fupporting the conclufion by the premises, and the premises again by the conclufion. Nor can there be an infinite number of middle terms between the firit principle and the conclufion.

In all demonstration, the first principles, the conclufion, and all the intermediate propofitions, must be neceffary, general, and eternal truths for of things fortuitous, contingent, or mutable, or of individual things, there is no demonstration.

Some demonftrations prove only, that the thing is thus affected; others prove, why it is thus affected. The former may be drawn from a remote caufe, or from an effect: but the latter must be drawn from an immediate caufe; and are the most perfect.

The first figure is beft adapted to demonstration, because it affords conclufions univerfally affirmative; and this figure is commonly used by the mathematicians.

The demonstration of an affirmative propofition is preferable to that of a negative; the demonstration of an univerfal to that of a particular; and direct demonstration to that ad abfurdum.

The principles are more certain than the conclufion.

There cannot be opinion and science of the fame thing at the fame time.

In the fecond book we are taught, that the questions that may

be

1. Whether the

2. Why it is thus affected. 3. Whether

The last of these questions Aristotle, in good Greek, calls the What is it of a thing. The fchoolmen, in very barbarous Latin, called this, the quiddity of a thing. This quiddity, he proves by many arguments, cannot be demonftrated, but must be fixed by a definition. This gives occafion to treat of definition, and how a right definition should be formed. As an example he gives a definition of the number three, and defines it to be the first odd number.

In this book he treats alfo of the four kinds of causes; efficient, material, formal, and final.

Another thing treated of in this book is, the manner in which we acquire first principles, which are the foundation of all demonstration. These are not innate, because we may be for a great part of life ignorant of them: nor can they be deduced demonftratively from any antecedent knowledge, otherwife they would not be first principles. Therefore he concludes, that first principles are got by induction, from the informations of fenfe. The fenfes give us informations of individual things, and from thefe by induction we draw general conclufions: for it is a maxim with Aristotle, That there is nothing in the understanding which was not before in some sense.

The knowledge of first principles, as it is not acquired by demonstration, ought not to be called fcience; and therefore he calls it intelligence.

SECT.

1

SECT. 2. Of the Topics.

The profeffed defign of the Topics is, to fhew a method by which a man may be able to reason with probability and confiftency upon every question that may occur.

Every question is either about the genus of the fubject, or its specific difference, or fome thing proper to it, or fomething accidental,

If

To prove that this divifion is complete, Ariftotle reasons thus: Whatever is attributed to a fubject, it must either be, that the fubject can be reciprocally attributed to it, or that it cannot. the fubject and attribute can be reciprocated, the attribute either declares what the subject is, and then it is a definition; or it does not declare what the subject is, and then it is a property. If the attribute cannot be reciprocated, it must be fomething contained in the definition, or not. If it is contained in the definition of the fubject, it must be the genus of the fubject, or its specific difference; for the definition confifts of these two. If it is not contained in the definition of the fubject, it must be an accident.

The furniture proper to fit a man for arguing dialectically may be reduced to these four heads: 1. Probable propofitions of all forts, which may on occafion be affumed in an argument. 2. Diftinctions of words which are nearly of the fame fignification. 3. Distinctions of things which are not fo far asunder but that they be taken for one and the fame. 4. Similitudes. The fecond and the five following books are taken up in enumerating the topics or heads of argument that may be used in questions about the genus, the definition, the properties, and the accidents of a thing; and occafionally he introduces the topics for

may

proving

proving things to be the fame, or different; and the topics for proving one thing to be better or worse than another.

In this enumeration of topics, Ariftotle has fhewn more the fertility of his genius, than the accuracy of method. The writers of logic seem to be of this opinion: for I know none of them that has followed him closely upon this fubject. They have confidered the topics of argumentation as reducible to certain axioms. For instance, when the question is about the genus of a thing, it must be determined by some axiom about genus and fpecies; when it is about a definition, it must be determined by fome axiom relating to definition, and things defined and fo of other questions. They have therefore reduced the doctrine of the topics to certain axioms or canons, and disposed these axioms in order under certain heads.

This method feems to be more commodious and elegant than that of Aristotle. Yet it must be acknowledged, that Aristotle has furnished the materials from which all the logicians have borrowed their doctrine of topics: and even Cicero, Quintilian, and other rhetorical writers, have been much indebted to the topics of Aristotle.

He was the first, as far as I know, who made an attempt of this kind: and in this he acted up to the magnanimity of his own genius, and that of ancient philofophy. Every fubject of human thought had been reduced to ten categories; every thing that can be attributed to any fubject, to five predicables: he attempted to reduce all the forms of reafoning to fixed rules of figure and mode, and to reduce all the topics of argumentation under certain heads; and by that means to collect as it were into one store all that can be faid on one fide or the other of every question, and provide a grand arsenal, from which all future combatants might be furnithed with arms offenfive and defenfive in every cause, so as to leave no room to future generations to invent any thing new.

The

The last book of the Topics is a code of the laws, according to which a fyllogistical difputation ought to be managed, both on the part of the affailant and defendant. From which it is evident, that this philofopher trained his difciples to contend, not for the truth merely, but for victory.

SECT. 3. Of the book concerning Sophifms.

A fyllogifm which leads to a false conclufion, must be vicious, either in matter or form: for from true principles nothing but truth can be juftly deduced. If the matter be faulty, that is, if either of the premises be false, that premise must be denied by the defendant. If the form be faulty, fome rule of fyllogifm is tranfgreffed; and it is the part of the defendant to fhew, what general or special rule it is that is tranfgreffed. So that, if he is an able logician, he will be impregnable in the defence of truth, and may refift all the attacks of the fophift. But as there are fyllogifms which may feem to be perfect both in matter and form, when they are not really fo, as a piece of money may seem to be good coin, when it is adulterate; fuch fallacious fyllogifms are confidered in this treatise, in order to make a defendant more expert in the ufe of his defenfive weapons.

And here the author, with his ufual magnanimity, attempts to bring all the fallacies that can enter into a fyllogifm under thirteen heads; of which fix lie in the diction or language, and seven not in the diction.

The fallacies in diction are, 1. When an ambiguous word is taken at one time in one fenfe, and at another time in another. 2. When an ambiguous phrafe is taken in the fame manner. 3. and 4. are ambiguities in fyntax; when words are conjoined in fyntax that ought to be disjoined; or disjoined when they

ought