=9. POSITIVE AND NEGATIVE TERMS.= _A positive term is one which signifies the possession of certain attributes_; e. g., metal, man, teacher, happy, honest. _A negative term is one which signifies the absence of certain attributes_; e. g., inorganic, unhappy, non-metallic. Terms which have the prefix not, non, un, in, dis, etc., or the affix less, are usually considered negative. The fact that there are some exceptions to this must not be overlooked. For example, unloosed, invaluable, are positive terms. In theory every positive term has its corresponding negative; as pure, impure; organic, inorganic; metal, non-metal; good, not-good. In some instances the language does not supply the word with the negative prefix because no need of it has been felt. The only way to express the negative of such words as good, table, etc., is to prefix “not” or “non.” =10. CONTRADICTORY AND OPPOSITE TERMS. (See page 38).= Positive terms with their negatives have contradictory meanings and therefore are referred to as contradictory terms. For example, honest and not-honest, metallic and non-metallic, perfect and imperfect, are contradictory terms. Such terms are mutually destructive. When we assert the truth of one we also imply the falsity of the other. If, for example, we assert that Abraham Lincoln was honest, we carry with this assertion the implication that Lincoln was not not-honest, or that any statement to the effect that he was not honest is false. Contradictory terms, when used in a sentence, illustrate the law of excluded middle, as in the statements: “John’s recitation is either perfect or imperfect.” “This teacher is either just or not-just.” There is no middle ground in such propositions. When contradictory terms are used in classification the whole is divided into but two classes; e. g.: honest not-honest agreeable not-agreeable metallic non-metallic perfect imperfect pure impure organic inorganic All the men in the world are either honest or not-honest. All the substances in existence are either organic or inorganic, etc. It will also be seen from this list that the contradictory of the positive form is not always indicated by using the prefix. Honest and dishonest, or agreeable and disagreeable, are not contradictory terms. In the case of agreeable and disagreeable, there seems to be the middle ground of absolute indifference. For example: the music of the orchestra is agreeable while the humming of the enthusiast back of me is decidedly disagreeable; but as to the noise upon the street, it is neither agreeable nor disagreeable as long practice has made me indifferent to it. When there is any doubt as to the terms being contradictory, the safest plan is to prefix “not” or “non” to the positive form. Terms which oppose each other but do not contradict are said to be opposite or contrary terms. The following list illustrate opposite terms: