The foregoing has hopefully filled in enough background that we can begin to make sense of the more mysterious parts of CP 3.73.
The Signs for Multiplication (cont.)
Thus far, we have considered the multiplication of relative terms only. Since our conception of multiplication is the application of a relation, we can only multiply absolute terms by considering them as relatives.
Now the absolute term “man” is really exactly equivalent to the relative term “man that is ──”, and so with any other. I shall write a comma after any absolute term to show that it is so regarded as a relative term.
Then “man that is black” will be written:
(Peirce, CP 3.73)
In any system where elements are organized according to types, there tend to be any number of ways in which elements of one type are naturally associated with elements of another type. If the association is anything like a logical equivalence, but with the first type being lower and the second type being higher in some sense, then one may speak of a semantic ascent from the lower to the higher type.
For example, it is common in mathematics to associate an element of a set with the constant function that has for all in where is an arbitrary set that is fixed in the context of discussion. Indeed, the correspondence is so close that one often uses the same name to denote both the element in and the function relying on context or an explicit type indication to tell them apart.
For another example, we have the tacit extension of a -place relation to a -place relation that we get by letting that is, by maintaining the constraints of on the first variables and letting the last variable wander freely.
What we have here, if I understand Peirce correctly, is another such type of natural extension, sometimes called the diagonal extension. This extension associates a -adic relative or a -adic relation, counting the absolute term and the set whose elements it denotes as the cases for with a series of relatives and relations of higher adicities.
A few examples will suffice to anchor these ideas.