It is easy to use opposite terms in a contradictory sense. This leads to serious error. “Not-guilty” is the contradictory of “guilty,” while “innocent” is the opposite of “guilty.” We could hardly say that the water must either be cold or hot, as it might be warm. “Not-hot” is the only term which contradicts “hot.” The law of contradiction has nothing to do with opposites.

Further, it is dangerous to regard words with the negative prefix as being contradictory of the affirmative form. For example: Valuable and invaluable are not contradictory. There is likewise some doubt as to the contradictory nature of such words as agreeable and disagreeable, though we are sure that agreeable and not-agreeable contradict each other. To use the “not” with a hyphen is safer than to depend upon some prefix which is supposed to mean “not.”

ILLUSTRATIONS OF CONTRADICTORY AND OPPOSITE TERMS.

Opposite. Contradictory.
badgood badnot-bad
softhard softnot-soft
coldhot coldnot-cold
roughsmooth roughnot-rough
goodevil goodnot-good
warmcool warmnot-warm
weakstrong weaknot-weak

4. THE LAW OF EXCLUDED MIDDLE.

The law of excluded middle may be considered as a combination of identity and contradiction. Identity gives the proposition, “John Doe is honest.” Contradiction, “John Doe is not honest.” Combine the two using either and or and we have the excluded middle proposition, “Either John Doe is honest or he is not honest.”

Excluded middle explains itself. Of the two contradictory notions it must be either the one or the other. There is no “go-between” notion.

The law may be stated in many ways, as will be seen by the following: (1) Everything must either be or not be. (2) Either a given judgment is true or its contradictory is true; there is no middle ground. (3) Of two contradictory judgments one must be true. (4) Every predicate may be affirmed or denied of every subject.

ILLUSTRATIONS:

(1) A man is either mortal or he is not mortal. (2) John Doe is either honest or not-honest. (3) Either you are going or you are not going.