Aristotle defines syllogism as discourse in which certain
things being stated ,something other than what is stated following necessity
from their being so. This is the principle of implication and Aristotle was
particularly concerned that scientific discourse should proceed from one valid
step to another with precision. He wanted to discover the method that would guarantee that conclusions were
rightly inferred from their premises . Th thought that it is possible through
syllogism.
The syllogism represents a special form of connected
language. According to Aristotle scientific demonstrations are possible because
certain words stand for certain properties, qualities or characteristics of
things. Such words stand for essential
properties as compared with accidental properties. To say that a man is mortal is to describe
one of his essential properties, whereas to say that he has red hair is to
describe something accidental, since to be a man it is not necessary or
essential that to be have red or even any hair .
But it is essential
to his being a man that he be mortal ,and it is such essential properties of
things that scientific propositions look for. When we ask why it is that men
are mortal a fact we already know from
experience , we are asking for a scientific or technical “reason why”. It is at this point that the specially
connected language of the syllogism comes into operation, for the syllogism
represents the linking of propositions about essential properties in such a way
that the conclusion necessarily follows .
And what makes the conclusion follow
is that a particular term is found in both of the premises , linking these
premises together so that the conclusion necessarily follows. We say first that
“all animals are mortals” and next that ’ all men are animals’ and from this it
follows that “all men are mortals”. The middle term here is animals and this
term is linked to the predicate mortal and to the subject all men , thereby
producing the implication that “all men are mortal”. In a formal way, Aristotle sets up the
structure of the syllogism as follows;
If (A) is predicated of all (B) which is a major premise;
and
(B) is predicated of
all (C) which is a minor premise then
(A) is necessarily
predicated of all (C) which is conclusion;
Aristotle’s chief interest in developing the syllogism is
not simply to assure consistent reasoning but to provide an instrument for
scientific demonstrations, and for this reason, again, he emphasized the
relation between logic and metaphysics, between our way of knowing and what
things are and how they behave. Aristotle, however, distinguished between three
kinds of reasoning, each of which might use the instrument of the syllogion but
with different results; these are ,first, dialectical reasoning ,which is
reassuming from “opinion that are generally accepted” second, there is eristic
or contentious reassuming ,which begins
with opinions that seem to be generally accepted but are really not, and, third
, there is what Aristotle calls demonstrative
reasoning where the premise from which reasoning Starts are true and
primary.
The value of syllogistic reasoning depended for Aristotle
upon the accuracy of the premises;