Perhaps, however, the second form of demonstration, that which
proceeds from truths better known to us, is not demonstration in the
unqualified sense of the term.
The advocates of circular demonstration are not only faced with
the difficulty we have just stated: in addition their theory reduces
to the mere statement that if a thing exists, then it does exist-an
easy way of proving anything. That this is so can be clearly shown
by taking three terms, for to constitute the circle it makes no
difference whether many terms or few or even only two are taken.
Thus by direct proof, if A is, B must be; if B is, C must be;
therefore if A is, C must be. Since then-by the circular proof-if A
is, B must be, and if B is, A must be, A may be substituted for C
above. Then 'if B is, A must be'='if B is, C must be', which above
gave the conclusion 'if A is, C must be': but C and A have been
identified. Consequently the upholders of circular demonstration are
in the position of saying that if A is, A must be-a simple way of
proving anything. Moreover, even such circular demonstration is
impossible except in the case of attributes that imply one another,
viz.
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