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- They say that the study of syllogisms is extremely useful; for it
indicates what is demonstrative, and this makes a big contribution towards
correcting one's opinions; and orderliness and good memory indicate
attentive comprehension. And an argument itself is a complex [made up
of] premisses and a conclusion; and a syllogism is a syllogistic argument
[made up] of these. And demonstration is an argument which by means
of things more [clearly] grasped concludes to something which is less
[clearly] grasped.
A presentation is an impression in a soul, the name being appropriately
transferred from the imprints in wax made by a seal-ring. - Of presentations, some are graspable, some non-graspable. The
graspable presentation, which they say is the criterion of facts [pragmata ],
is that which comes from an existing object, and is stamped and moulded
in accordance with the existing object itself. The non-graspable presenta-
tion is either not from an existing object, or from an existing object but not
in accordance with it; it is neither clear nor well-stamped [i.e., distinct].
Dialectic itself is necessary and is a virtue which contains other virtues
as species. And freedom from hasty judgement is knowledge of when
one ought to assent and when not. And level-headedness is a strong-
minded rationality with respect to what is likely, so that one does not
give in to it. - And irrefutability is strength in argument, so that one is not swept
away by it to an opposite opinion. And intellectual seriousness is a
disposition which refers presentations to right reason. Knowledge itself,
they say, is either a secure grasp or a disposition in the reception of
presentations not reversible by argument. And the wise man will not be
free of error in argument without the study of dialectic. For truth and
falsity are distinguished by it and persuasive and ambiguous statements
are properly discerned by it. And without it methodical question and
answer are impossible. - Hasty judgement in assertions has an impact on events, so that
those who are not well exercised in handling presentations turn to unruli-
ness and aimlessness. And there is no other way for the wise man to show
himself to be sharp, quick-witted and, in general, clever in arguments. For
the same man will be able to converse properly and reason things out
and also take a position on issues put to him and respond to questions-
these are characteristics of a man experienced in dialectic.
So, this is a summary of their doctrines in logic; and in order to
give a detailed account also of those of their views which pertain to an
introductory textbook, verbatim exactlyDiodes
of Magnesia includes in his Survey of Philosophers, writing as follows. - The Stoics choose to put first the account of presentation and