It has been observed that the species refers to more qualities than the genus. In fact, it represents all the attributes of the genus plus those which distinguish the particular species from the other species of the genus. These additional qualities are the differentiæ of the particular species. TO ILLUSTRATE: The attribute which distinguishes man from the other bipeds of the world is his rationality. That which distinguishes the rectangle from the other parallelograms is its four right angles. The attributes _rationality_ and _right angles_ are differentiae. (4) _Property._ _A property of a term is any attribute which helps to make the term what it is._ Thus “consciousness” is a property of man, “binding” a property of book, “angles” a property of triangle. Deprive the terms of these attributes and their true nature is altered. A differentia is a property according to the foregoing definition. However, Jevons defines “property” as “Any quality which is common to the whole of a class, but is not necessary to mark out the class from other classes.” This viewpoint excludes “differentia” from the notion of property. The difference in opinion is of slight importance. (5) _Accident._ _An accident of a term is any attribute which does not help to make the term what it is._ It may indifferently belong or not belong to the term. Deprive a term of an accident and the nature of the term remains unchanged. Thus, a teacher’s position, a man’s watch, the fact that the angle is one of 80° are all accidents. It is obvious that a property is a _constant_ attribute while an accident is variable. This gives to the former a universal validity while the latter is more or less shifting and uncertain. All triangles must have _three angles_ (property) while the _value of each angle in degrees_ (accident) admits of unlimited variation. Some logicians divide accidents into separable and inseparable. A man’s _hat_ would be a separable accident while his _birthplace_ would be an inseparable accident. FIVE PREDICABLES ILLUSTRATED. In the following brief descriptions the five predicables are designated: (species) (genus) (differentia) (1) This ――――――――― is a ――――――――――――― with ――――――――――――――――― rectangle parallelogram four right angles (accident) its longer sides being ――――――――――. ten inches (species) (differentia) (prox. genus) (2) This ――――――――― is a ――――――――――――― ――――――――――――― with the man rational biped (property) (accident) ――――――――――――――――――― and a ――――――――――――――――. power of locomotion ruddy complexion