(3) _The middle term must be distributed at least once._ The rule is usually given in this way, “The middle term must be distributed once at least, and must not be ambiguous.” In this treatment the last part of the rule has been omitted because it must be apparent to the student that a middle term used in two senses is virtually equivalent to _two different terms_; such an “ambiguous middle” would, in consequence, give a syllogism of _four terms_. Rules 3 and 4 are of greater importance than the others because they are more frequently violated. If the middle term is not distributed at least once, the fallacy is referred to as “_undistributed middle_.” If the distributed major term of the conclusion is not distributed in the major premise, then the fallacy is called, “_illicit process of the major term_”; and finally, if the distributed minor term of the conclusion is not distributed in the minor premise the fallacy is denominated an “_illicit process of the minor term_.” These two illicit processes may be abbreviated to illicit major and illicit minor. Recall that any term is distributed when it is referred to as a definite whole. Unless the whole of the middle term is considered it fails to become a common standard of comparison. This becomes clear when recourse is made to the circles. _Illustration._ Syllogism in which the middle term is not distributed: All men are mortal, All trees are mortal, ∴ All trees are men. All the propositions are A’s and consequently the predicates of each are undistributed, as A distributes the subject _only_. Therefore the middle term, “_mortal_,” is not distributed in either of the premises and thus the fallacy. Fallacy shown by circles: Illustration: FIG. 9. These circles indicate the correct meaning of the two premises. By them it is seen that all of the “men” circle belongs to the “mortal” circle and all of the “tree” circle belongs to the “mortal” circle, but in this case there is no connection between the “men” and “tree” circles. Thus, to say that “_All trees are men_,” is fallacious. We have no right to either affirm or deny the connection between men and trees. If “mortal” were distributed we would have this right as the following will make clear: All men are mortal, No stones are mortal, ∴ No stones are men. Illustration: FIG. 10. Here the middle term _mortal_ is distributed in the second premise as in it the subject “_stones_” is _excluded_ from the entire mortal territory. This conclusion is verified by the formal statement that “E” distributes both subject and predicate. Since all of the “men” circle belongs to the “mortal” circle and none of the “stones” circle belongs to the “mortal” circle then none of the “stones” circle can belong to the “men” circle. (4) _No term must be distributed in the conclusion which is not also distributed in its premise._