Second antecedent judgment: Socrates was a man. S was m ――――――― Conclusion: Socrates was fallible. ∴ S was f Giving attention to the antecedent judgments of the second argument it is noted that the terms “_f_” and “_S_” are referred to the common term “_m_.” In logic this common term is known as the _middle term_. As there is but one antecedent judgment in the first argument there can be no common or middle term. The first argument is an illustration of _immediate_ inference; the second of _mediate_ inference. This suggests the definitions: _Immediate inference is inference without the use of a middle term._ _Mediate inference is inference by means of a middle term._ =3. THE FORMS OF IMMEDIATE INFERENCE.= Many logicians recognize four forms of immediate inference. These four forms are (1) _opposition_, (2) _obversion_, (3) _conversion_, (4) _contraversion._[8] (1) _IMMEDIATE INFERENCE BY OPPOSITION._ We have learned that to be logical all categorical assertions must be reduced to some one of the four propositions, A, E, I, O. If these four logical propositions be given the _same subject and predicate_, certain definite relations will become evident; therefore, _Opposition is said to exist between propositions which are given the same subject and predicate, but differ in quality, or in quantity, or in both_. The following illustrative outline will make this clear: 1. _Original Proposition._ I. All men are mortal. (A) II. No men are immortal. (E) III. Some men are wise. (I) IV. Some men are mortal. (I) V. Some men are not wise. (O) VI. Some men are not immortal. (O) 2. _Opposite in Quantity._ I. Some men are mortal. (I) II. Some men are not immortal. (O) III. All men are wise. (A) IV. All men are mortal. (A) V. No men are wise. (E) VI. No men are immortal. (E) 3. _Opposite in Quality._ I. No men are mortal. (E) II. All men are immortal. (A) III. Some men are not wise. (O) IV. Some men are not mortal. (O) V. Some men are wise. (I) VI. Some men are immortal. (I) 4. _Opposite in Both._ I. Some men are not mortal. (O) II. Some men are immortal. (I) III. No men are wise. (E) IV. No men are mortal. (E) V. All men are wise. (A) VI. All men are immortal. (A)