The Complete Aristotle (eng.)

characters belong in a particular respect,
then, they say, ‘contrary attributes belong at the same time’. This
kind of thing is in some cases easily seen by any one, e.g. suppose
a man were to secure the statement that the Ethiopian is black, and
were then to ask whether he is white in respect of his teeth; and
then, if he be white in that respect, were to suppose at the
conclusion of his questions that therefore he had proved
dialectically that he was both white and not white. But in some
cases it often passes undetected, viz. in all cases where, whenever
a statement is made of something in a certain respect, it would be
generally thought that the absolute statement follows as well; and
also in all cases where it is not easy to see which of the
attributes ought to be rendered strictly. A situation of this kind
arises, where both the opposite attributes belong alike: for then
there is general support for the view that one must agree
absolutely to the assertion of both, or of neither: e.g. if a thing
is half white and half black, is it white or black?
    Other fallacies occur because the terms ‘proof’ or ‘refutation’
have not been defined, and because something is left out in their
definition. For to refute is to contradict one and the same
attribute-not merely the name, but the reality-and a name that is
not merely synonymous but the same name-and to confute it from the
propositions granted, necessarily, without including in the
reckoning the original point to be proved, in the same respect and
relation and manner and time in which it was asserted. A ‘false
assertion’ about anything has to be defined in the same way. Some
people, however, omit some one of the said conditions and give a
merely apparent refutation, showing (e.g.) that the same thing is
both double and not double: for two is double of one, but not
double of three. Or, it may be, they show that it is both double
and not double of the same thing, but not that it is so in the same
respect: for it is double in length but not double in breadth. Or,
it may be, they show it to be both double and not double of the
same thing and in the same respect and manner, but not that it is
so at the same time: and therefore their refutation is merely
apparent. One might, with some violence, bring this fallacy into
the group of fallacies dependent on language as well.
    Those that depend on the assumption of the original point to be
proved, occur in the same way, and in as many ways, as it is
possible to beg the original point; they appear to refute because
men lack the power to keep their eyes at once upon what is the same
and what is different.
    The refutation which depends upon the consequent arises because
people suppose that the relation of consequence is convertible. For
whenever, suppose A is, B necessarily is, they then suppose also
that if B is, A necessarily is. This is also the source of the
deceptions that attend opinions based on sense-perception. For
people often suppose bile to be honey because honey is attended by
a yellow colour: also, since after rain the ground is wet in
consequence, we suppose that if the ground is wet, it has been
raining; whereas that does not necessarily follow. In rhetoric
proofs from signs are based on consequences. For when rhetoricians
wish to show that a man is an adulterer, they take hold of some
consequence of an adulterous life, viz. that the man is smartly
dressed, or that he is observed to wander about at night. There
are, however, many people of whom these things are true, while the
charge in question is untrue. It happens like this also in real
reasoning; e.g. Melissus’ argument, that the universe is eternal,
assumes that the universe has not come to be (for from what is not
nothing could possibly come to be) and that what has come to be has
done so from a first beginning. If, therefore, the universe has not
come to be, it has no first beginning, and is therefore eternal.
But this does not necessarily follow: for even if what has come to
be always has a first beginning, it does not also follow that what
has a first beginning has come to be; any more than it follows that
if a man in a fever be hot, a man who is hot must be in a
fever.
    The refutation which depends upon treating as cause what is not
a cause, occurs whenever what is not a cause is inserted in the
argument, as though the refutation depended upon it. This kind of
thing happens in arguments that reason ad impossible: for in these
we are bound to