Handbook of the History of Logic: - Fordham University Faculty

The Assimilation of Aristotelian and Arabic Logic up to the Later Thirteenth Century 289
if something A is essential to something else B, then this means that B cannot be
posited to exist without also A being posited to exist. If a human is posited to
exist, then an animal is also posited to exist.
Accidents are separated in the standard way into two different kinds, namely
separable accidents and inseparable accidents. The examples he gives of separable
and inseparable accidents are youth of a human being and blackness of an
Ethiopian (a very common example found in Porphyry’s Isagoge). In one case the
accident is separable from the substance, but in the other it is not.
Genus, species and difference (differentia) are crucial for definitions, Al-Ghazālī
explains, and it is only these three that can be said to fulfill the three criterion
above of essential relations or essential predication. A property (proprium) isnot
essential, according to Al-Ghazālī, since ‘A human being is able to laugh’ is not
an essential predication according to (3.1.10)-(3.1.12). It is hence an accidental
predication.
The longest part of the Maqāsid is on argumentation and it is divided into a
discussion of formal and material argumentation (or syllogisms). This distinction
is not entirely clear, although directly taken from Avicenna, and I will discuss it in
some detail below. I will first shortly deal with formal arguments, which is much
more straight-forward.
The part dealing with formal arguments is divided into syllogisms, induction,
and arguments by example. The part dealing with the syllogisms is divided into
categorical syllogisms and hypothetical syllogisms. Echoing Aristotle in the Prior
Analytics, he defines a syllogism in the following way:
A syllogism is a discourse in which statements are posited and granted,
and from which a statement other than those previously granted necessarily
follows. 23
This definition applies to both categorical and hypothetical syllogisms, and indeed
to all arguments.
The categorical syllogisms are at least initially given a standard presentation.
He mentions that it contains two propositions as premises and that the middle
term, which connects the two premises, are crucial for the production of a conclusion.
The middle term connects the major and minor terms, which are respectively
the predicate and subject of the conclusion. It is the order of these terms that
give the different syllogistic figures. Al-Ghazālī mentions three figures:
(Figure 1): The medium term is the predicate of one premise and
subject of the other.
(Figure 2): The medium term is the predicate of both premises.
(Figure 3): The medium term is the subject of both premises.
23 Al-Ghazālī, Tractatus de logica, 259, 18-9. Compare Aristotle’s definition in the Prior Analytics:
“A deduction (syllogism) is a discourse in which, certain things being stated, something
other than what is stated follows of necessity from their being so.” (24b19-20) The translation
is by Robin Smith.