Cf: Peirce’s 1870 “Logic of Relatives” • Comment 11.9
https://inquiryintoinquiry.com/2014/05/07/peirces-1870-logic-of-relatives-c…
Peirce’s 1870 “Logic of Relatives” • Comment 11.9
https://oeis.org/wiki/Peirce%27s_1870_Logic_Of_Relatives_%E2%80%A2_Part_2#C…
All,
Among the variety of regularities affecting dyadic relations
we pay special attention to the c-regularity conditions where
c is equal to 1.
Let P ⊆ X × Y be an arbitrary dyadic relation.
The following properties can be defined.
Definitions 1
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We previously examined dyadic relations exemplifying each of these
regularity conditions. Then we introduced a few bits of terminology
and special-purpose notations for working with tubular relations.
Definitions 2
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We arrive by way of this winding stair at the special cases of
dyadic relations P ⊆ X × Y variously described as “1-regular”,
“total and tubular”, or “total prefunctions” on specified domains,
X or Y or both, and which are more often celebrated as “functions”
on those domains.
If P is a pre-function P : X ⇀ Y that happens to be total at X
then P is known as a “function” from X to Y, typically indicated
as P : X → Y.
To say a relation P ⊆ X × Y is “total and tubular” at X
is to say P is 1-regular at X. Thus, we may formalize
the following definitions.
Definitions 3
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For example, let X = Y = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} and let
F ⊆ X × Y be the dyadic relation depicted in the bigraph below.
Figure 39. Dyadic Relation F
https://inquiryintoinquiry.files.wordpress.com/2014/05/lor-1870-figure-39.j…
We observe that F is a function at Y and we record this
fact in either of the manners F : X ← Y or F : Y → X.
Regards,
Jon