Descartes, Rene - Entities and entity sub-types
Type of Spiritual Experience
In a generic sense this is about classes and sub-classes, entities and entity sub-types; but Descartes is also applying the same principles to the tree of life.
He then notes that functions - in this case arithmetical functions - apply to entities and entity sub-types. That really a property is just nother name for a function, once we have established the class and thr attribute that distinguishes that class.
A description of the experience
Rene Descartes – Key Philosophical Writings
and in the same way when we consider a three sided figure we form a certain idea which we call the idea of a triangle; and we afterwards make use of it as a universal in representing to ourselves all the figures having three sides. But when we notice more particularly that of three sided figures some have a right angle and some have not, we form the universal idea of a rectangular triangle, which being related to the preceding as to a more general may be termed a species; and the right angle is the universal difference by which right angled triangles are distinguished from all others.
If we further observe that the square of the side which subtends the right angle is equal to the square of the other two sides, and that this property belongs only to this species of triangle, we may term it a universal property of the species.
Finally if we suppose that certain of the triangles are moved, and others are not moved we should take that to be a universal accident of the same; and it is thus that we commonly enumerate the five universals – genus, species, difference, property, accident.