On to the next part of §3. Application of the Algebraic Signs to Logic.

Peirce’s 1870 “Logic of Relatives” • Selection 5

Peirce in 1870 is five years down the road from the Peirce of 1865–1866 who lectured extensively on the role of sign relations in the logic of scientific inquiry, articulating their involvement in the three types of inference, and inventing the concept of “information” to explain what it is that signs convey in the process.  By this time, then, the semiotic or sign relational approach to logic is so implicit in his way of working that he does not always take the trouble to point out its distinctive features at each and every turn.  So let’s take a moment to draw out a few of those characters.

Sign relations, like any brand of non-trivial triadic relations, can become overwhelming to think about once the cardinality of the object, sign, and interpretant domains or the complexity of the relation itself ascends beyond the simplest examples.  Furthermore, most of the strategies we’d normally use to control the complexity, like neglecting one of the domains, in effect, projecting the triadic sign relation onto one of its dyadic faces, or focusing on a single ordered triple at a time, can result in our receiving a distorted impression of the sign relation’s true nature and structure.

I find it helps me to draw, or at least to imagine drawing, diagrams of the following form, where I can keep tabs on what’s an object, what’s a sign, and what’s an interpretant sign, for a selected set of sign-relational triples.

Figure 1 shows how I would picture Peirce’s example of equivalent terms, where denotes the Vice-President of the United States, and denotes the President of the Senate of the United States.

Depending on whether we interpret the terms and as applying to persons who hold the offices at one particular time or as applying to all persons who have held the offices over an extended period of history, their denotations may be either singular of plural, respectively.

Terms referring to many objects are known as having general denotations or plural referents.  They may be represented in the above style of picture by drawing an ellipsis of three nodes like “o o o” at the object ends of sign relational triples.

For a more complicated example, Figure 2 shows how I would picture Peirce’s example of an equivalence between terms which comes about by applying the distributive law for relative multiplication over absolute summation.

Resources

• Peirce’s 1870 Logic of Relatives • Part 1 • Part 2 • Part 3 • References

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