§ 643. The canon of the fourth figure has had no name assigned to it, and does not seem to admit of any simple expression. Another mode of formulating it is as follows:—
Whatever is affirmed of a whole term may have partially affirmed of it whatever is included in that term (Bramantip, Dimaris), and partially denied of it whatever is excluded (Fesapo); whatever is affirmed of part of a term may have partially denied of it whatever is wholly excluded from that term (Fresison); and whatever is denied of a whole term may have wholly denied of it whatever is wholly included in that term (Camenes).
§ 644. From the point of view of intension the canons of the first three figures may be expressed as follows.
§ 645. Canon of the first figure. Dictum de Omni et Nullo—
An attribute of an attribute of anything is an attribute of the thing itself.
§ 646. Canon of the second figure. Dictum de Diverso—
If a subject has an attribute which a class has not, or vice versa, the subject does not belong to the class.
§ 647. Canon of the third figure.
1. Dictum de Exemplo—
If a certain attribute can be affirmed of any portion of the members of a class, it is not incompatible with the distinctive attributes of that class.