28. Again, the violation of the law of contradiction does not
involve any violation of the law of identity: for a thing might in
that case be still itself, so that the law of identity would be
observed, even though, owing to the law of contradiction not holding,
it were not itself at the same time. Neither would the law of excluded
middle be infringed. For a thing would, on the supposition, be both
itself and not itself, which is the very reverse of being neither.

29. Lastly, the law of excluded middle might be violated without a
violation of the law of contradiction: for we should then have a thing
which was neither A nor not A, but not a thing which was both at the
same time. Neither would the law of identity be infringed. For we
should in this case have a thing which neither was nor was not, so
that the conditions of the law of identity could not exist to be
broken. That law postulates that whatever is, is: here we have a thing
which never was to begin with.

30. These principles are of so simple a character that the
discussion of them is apt to be regarded as puerile. Especially is
this the case with regard to the law of identity. This principle in
fact is one of those things which are more honoured in the breach than
in the observance. Suppose for a moment that this law did not
hold--then what would become of all our reasoning? Where would be the
use of establishing conclusions about things, if they were liable to
evade us by a Protean change of identity?

31. The remaining two laws supplement each other in the following
way. The law of contradiction enables us to affirm of two exhaustive
and mutually exclusive alternatives, that it is impossible for both to