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IN the First Analytics, fyllogisms are con
fidered in respect of their form ; they are now to be considered in respect of their
The form lies in the necessary connection between the premises and the conclusion; and where such a connection is wanting, they are said to be informal, or vicious in point of form.
But where there is no fault in the form, there may
be in the matter; that is, in the propositions of which they are composed, which may be true or false, probable or improbable
When the premises are certain, and the conclusion drawn from them in due form, this is demonstration, and produces scio ence. Such fyllogisms are called apodica
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tical; and are handled in the two books of the Last Analytics. When the premises are not certain, but probable only, such fyllogisins are called dialectical; and of them he treats in the eight books of the Topics. But there are some fyllogisms which seem to be perfect both in matter and form, when they are not really so: as, a face may seem beautiful which is but painted. These being apt to deceive, and produce a false opinion, are called fophiftical; and they are the subject of the book concerning Sophisms.
To return to the Last Analytics, which treat of demonstration and of science: We ihall not pretend to abridge these books; for Aristotle's writings do not admit of abridgement: no man in fewer words can say what he says; and he is not often guilty of repetition. We shall only give some of his capital conclusions, 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 same kind; until we come at last to first principles, which neither
can be demonstrated, nor need to be, being evident of themselves.
We cannot demonstrate things in a circle, supporting the conclusion by the premises, and the premises by the conclufion. Nor can there be an infinite number of middle terms between the first principle and the conclusion.
In all demonstration, the first principles, the conclusion, and all the intermediate propositions, must be necessary, general, and eternal truths: for of things fortuitous, contingent, or mutable, or of individual things, there is no demonstration.
Some demonstrations prove only, that the thing is thus affected; others prove, why it is thus affected. The former may be drawn from a remote cause, or from an effect: but the latter must be drawn from an immediate cause; and are the most perfect.
The first figure is best adapted to demonstration, because it affords conclufions universally affirmative; and this figure is commonly used by the mathematicians.
The demonstration of an affirmative proposition is preferable to that of a nega
tive; the demonstration of an universal to that of a particular; and direct demonstration to that ad absurdum.
The principles are more certain than the conclusion.
There cannot be opinion and science of the same thing at the same time.
In the second book we are taught, that the questions that may
with regard to any thing, are four: 1. Whether the thing be thus affected. 2. Why it is thus affected. 3. Whether it exists. 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 demonstrated, but must be fixed by a definition. This gives occasion to treat of definition, and how a righe 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 also 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 prin-
The knowledge of first principles, as it
Sect. 2. Of the Topics.
The professed design of the Topics is, to Thew a method by which a man may be able to reason with probability and con