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tive; the demonstration of an univerfal to that of a particular; and direct demonftration 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 put with regard to any thing, are four: 1. Whether the thing be thus affected. 2. Why it is thus affected. 3. Whether it exists. 4. What

it is.

The last of these questions Aristotle, in good Greek, calls the What is it of a thing. The schoolmen, 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 firft odd number.

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

Another thing treated of in this book is,


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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 these 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 fome fense.

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

SECT. 2. Of the Topics.

The profeffed defign of the Topics is, to fhew a method by which a man may be able to reafon with probability and con


fiftency upon every question that can oc


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

To prove that this divifion is complete, Aristotle 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. If 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 be contained in the definition of the subject, it must be the genus of the fubject, or its specific difference; for the definition confifts of these two. If it be 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. which are nearly of the fame fignification. 3. Diftinctions of things which are not fo far afunder but that they may be taken for one and the fame. 4. Similitudes.

2. Diftinctions of words

The second 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 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, Aristotle has fhewn more the fertility of his genius, than the accuracy of method. The writers of logic feem 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 inftance, when the queftion is about the genus thing, it must be determined by fome 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. VOL. III. They

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They have therefore reduced the doctrine of the topics to certain axioms or canons, and difpofed these axioms in order under certain heads.

This method feems to be more commodious and elegant than that of Ariftotle. 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 subject, to five predicables: he attempted to reduce all the forms of reasoning 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 to provide a grand arfenal, from

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