As a matter of fact and common sense, if we affirm any term of a Subject, we are bound to deny of that Subject, in the same relation, not only the contradictory but all synonyms for this, and also all contraries and opposites; which, of course, are included in the contradictory.

But who shall determine what these are?
Without an authoritative Logical Dictionary to refer to, where all contradictories, synonyms, and contraries may be found on record, Formal Logic will hardly sanction the free play of common sense.
The principle of Excluded Middle may be written: _B is either A or not-A_; that is, _if any term be denied of a subject, the contradictory term may, in the same relation, be affirmed_.

Of course, we may deny that a leaf is green on one side without being bound to affirm that it is not-green on the other.

But in the same relation a leaf is either green or not-green; at the same time, a stick is either bent or not-bent.

If we deny that A is greater than B, we must affirm that it is not-greater than B.
Whilst, then, the principle of Contradiction (that 'of contradictory predicates, one being affirmed, the other is denied ') might seem to leave open a third or middle course, the denying of both contradictories, the principle of Excluded Middle derives its name from the excluding of this middle course, by declaring that the one or the other must be affirmed.