If, on the other hand, we compare two judgments with the intention of bringing out the relation which the _subjects of both_ may have to each other, we must take as the common measure their predicate. This will accordingly be here the middle, and must therefore be the same in both judgments. Hence arises the _second figure_. In it the relation of two subjects to each other is determined by that which they have as their common predicate. But this relation can only have significance if the same predicate is attributed to the one subject and denied of the other, for thus it becomes an essential ground of distinction between the two. For if it were attributed to both the subjects this could decide nothing as to their relation to each other, for almost every predicate belongs to innumerable subjects. Still less would it decide this relation if the predicate were denied of both the subjects. From this follows the fundamental characteristic of the second figure, that the premisses must be of _opposite quality_; the one must affirm and the other deny. Therefore here the principal rule is: _Sit altera negans_; the corollary of which is: _E meris affirmativis nihil sequitur_; a rule which is sometimes transgressed in a loose argument obscured by many parenthetical propositions. The course of thought which this figure exhibits distinctly appears from what has been said. It is the investigation of two kinds of things with the view of distinguishing them, thus of establishing that they are _not_ of the same species; which is here decided by showing that a certain property is essential to the one kind, which the other lacks. That this course of thought assumes the second figure of its own accord, and expresses itself clearly only in it, will be shown by an example: All fishes have cold blood; No whale has cold blood: Thus no whale is a fish. In the first figure, on the other hand, this thought exhibits itself in a weak, forced, and ultimately patched-up form: Nothing that has cold blood is a whale; All fishes have cold blood: Thus no fish is a whale, And consequently no whale is a fish. Take also an example with an affirmative minor: No Mohamedan is a Jew; Some Turks are Jews: Therefore some Turks are not Mohamedans. As the guiding principle for this figure I therefore give, for the mood with the negative minor: _Cui repugnat nota, etiam repugnat notatum_; and for the mood with the affirmative minor: _Notato repugnat id cui nota repugnat_. Translated these may be thus combined: Two subjects which stand in opposite relations to one predicate have a negative relation to each other.