The Complete Aristotle (eng.)

problem is difficult and what sort is easy to prove. For
that which is concluded in many figures and through many moods is
easier; that which is concluded in few figures and through few
moods is more difficult to attempt. The universal affirmative is
proved by means of the first figure only and by this in only one
mood; the universal negative is proved both through the first
figure and through the second, through the first in one mood,
through the second in two. The particular affirmative is proved
through the first and through the last figure, in one mood through
the first, in three moods through the last. The particular negative
is proved in all the figures, but once in the first, in two moods
in the second, in three moods in the third. It is clear then that
the universal affirmative is most difficult to establish, most easy
to overthrow. In general, universals are easier game for the
destroyer than particulars: for whether the predicate belongs to
none or not to some, they are destroyed: and the particular
negative is proved in all the figures, the universal negative in
two. Similarly with universal negatives: the original statement is
destroyed, whether the predicate belongs to all or to some: and
this we found possible in two figures. But particular statements
can be refuted in one way only-by proving that the predicate
belongs either to all or to none. But particular statements are
easier to establish: for proof is possible in more figures and
through more moods. And in general we must not forget that it is
possible to refute statements by means of one another, I mean,
universal statements by means of particular, and particular
statements by means of universal: but it is not possible to
establish universal statements by means of particular, though it is
possible to establish particular statements by means of universal.
At the same time it is evident that it is easier to refute than to
establish.
    The manner in which every syllogism is produced, the number of
the terms and premisses through which it proceeds, the relation of
the premisses to one another, the character of the problem proved
in each figure, and the number of the figures appropriate to each
problem, all these matters are clear from what has been said.
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    We must now state how we may ourselves always have a supply of
syllogisms in reference to the problem proposed and by what road we
may reach the principles relative to the problem: for perhaps we
ought not only to investigate the construction of syllogisms, but
also to have the power of making them.
    Of all the things which exist some are such that they cannot be
predicated of anything else truly and universally, e.g. Cleon and
Callias, i.e. the individual and sensible, but other things may be
predicated of them (for each of these is both man and animal); and
some things are themselves predicated of others, but nothing prior
is predicated of them; and some are predicated of others, and yet
others of them, e.g. man of Callias and animal of man. It is clear
then that some things are naturally not stated of anything: for as
a rule each sensible thing is such that it cannot be predicated of
anything, save incidentally: for we sometimes say that that white
object is Socrates, or that that which approaches is Callias. We
shall explain in another place that there is an upward limit also
to the process of predicating: for the present we must assume this.
Of these ultimate predicates it is not possible to demonstrate
another predicate, save as a matter of opinion, but these may be
predicated of other things. Neither can individuals be predicated
of other things, though other things can be predicated of them.
Whatever lies between these limits can be spoken of in both ways:
they may be stated of others, and others stated of them. And as a
rule arguments and inquiries are concerned with these things. We
must select the premisses suitable to each problem in this manner:
first we must lay down the subject and the definitions and the
properties of the thing; next we must lay down those attributes
which follow the thing, and again those which the thing follows,
and those which cannot belong to it. But those to which it cannot
belong need not be selected, because the negative statement implied
above is convertible. Of the attributes which follow we must
distinguish those which fall within the definition, those which are
predicated as properties, and those which are predicated as
accidents, and of the latter those