What happened here is this. Our contemplation of a constant operator as being potentially variable gave rise to the contemplation of a newly introduced but otherwise quite ordinary operand variable, albeit in a newly-fashioned formula. In its interpretation for logic the newly formed operation may be viewed as an extension of ordinary negation, one in which the negation of the first variable is *controlled* by the value of the second variable. Thus, we may regard this development as marking a form of *controlled reflection*, or a form of *reflective control*. From here on out we will use the inline syntax for the corresponding operation on two variables, whose operation table is given below:

- The Entitative Interpretation for which Space = False and Cross = True, calls this operation
*equivalence*. - The Existential Interpretation for which Space = True and Cross = False, calls this operation
*distinction*.

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]]>The initial idea I had in mind was the same as before, that the operator over would be counted as absent when evaluates to a space and present when evaluates to a cross.

However, much in the same way that operators with a shade of negativity tend to be more generative than the purely positive brand, it turned out more useful to reverse this initial polarity of operation, letting the operator over be counted as absent when evaluates to a cross and present when evaluates to a space.

So that is the convention I’ll adopt from here on.

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]]>In the days when I scribbled these things on the backs of computer punchcards, the first thing I tried was drawing big loopy script characters, placing some inside the loops of others. Lower case alphas, betas, gammas, deltas, and so on worked best. Graphics like these conveyed the idea that a character-shaped boundary drawn around another space can be viewed as absent or present depending on whether the formal value of the character is unmarked or marked. The same idea can be conveyed by attaching characters directly to the edges of graphs.

Here is how we might suggest an algebraic expression of the form where the absence or presence of the operator depends on the value of the algebraic expression the operator being absent whenever is unmarked and present whenever is marked.

It was obvious to me from the outset that this sort of tactic would need a lot of work to become a usable calculus, especially when it came time to feed those punchcards back into the computer.

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]]>Then we asked the corresponding question about the operator The above selection of arithmetic expressions is what it means to contemplate the absence or presence of the operand in the algebraic expression But what would it mean to contemplate the absence or presence of the operator in the algebraic expression

Clearly, a variation between the absence and the presence of the operator in the algebraic expression refers to a variation between the algebraic expressions and respectively, somewhat as pictured below:

But how shall we signify such variations in a coherent calculus?

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]]>In this expression the variable name appears as an *operand name*. In functional terms, is called an *argument name*, but it’s best to avoid the potentially confusing connotations of the word *argument* here, since it also refers in logical discussions to a more or less specific pattern of reasoning.

As we discussed, the algebraic variable name indicates the contemplated absence or presence of any arithmetic expression taking its place in the surrounding template, which expression is proxied well enough by its formal value, and of which values we know but two. Thus, the given algebraic expression varies between these two choices:

The above selection of arithmetic expressions is what it means to contemplate the absence or presence of the operand in the algebraic expression But what would it mean to contemplate the absence or presence of the operator in the algebraic expression

That is the question I’ll take up next.

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]]>I found one key to the mystery in Peirce’s use of *operator variables*, which he and his students Christine Ladd-Franklin and O.H. Mitchell explored in depth. I will shortly discuss this theme as it affects logical graphs but it may be useful to give a shorter and sweeter explanation of how the basic idea typically arises in common logical practice.

Think of De Morgan’s rules:

We could capture the common form of these two rules in a single formula by taking and as variable names ranging over a set of logical operators, and then by asking what substitutions for and would satisfy the following equation:

We already know two solutions to this *operator equation*, namely, and Wouldn’t it be just like Peirce to ask if there are others?

Having broached the subject of *logical operator variables*, I will leave it for now in the same way Peirce himself did:

I shall not further enlarge upon this matter at this point, although the conception mentioned opens a wide field; because it cannot be set in its proper light without overstepping the limits of dichotomic mathematics. (*Collected Papers*, CP 4.306).

Further exploration of operator variables and operator invariants treads on grounds traditionally known as *second intentional logic* and “opens a wide field”, as Peirce says. For now, however, I will tend to that corner of the field where our garden variety logical graphs grow, observing the ways operative variations and operative themes naturally develop on those grounds.

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]]>For example, consider the following expression:

We may regard this algebraic expression as a general expression for an infinite set of arithmetic expressions, starting like so:

Now consider what this says about the following algebraic law:

It permits us to understand the algebraic law as saying, in effect, that every one of the arithmetic expressions of the contemplated pattern evaluates to the very same canonical expression as the upshot of that evaluation. This is, as far as I know, just about as close as we can come to a conceptually and ontologically minimal way of understanding the relation between an algebra and its corresponding arithmetic.

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]]>One of the things I added to the Survey this time around was an earlier piece of work titled “Futures Of Logical Graphs” (FOLG), which takes up a number of difficult issues in more detail than I’ve found the ability or audacity to do since. Among other things, it gives an indication of the steps I took from trees to cacti in the graph-theoretic representation of logical propositions and boolean functions, along with the forces that led me to make that transition.

A lot of the text goes back to the dusty old Ascii days of the discussion lists where I last shared it, so I’ll be working on converting the figures and tables and trying to make the presentation more understandable.

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]]>The blog post linked above updates my Survey of Resources for Animated Logical Graphs. It contains links to basic expositions and extended discussions of the graphs themselves, deriving from the *Alpha Graphs* C.S. Peirce used for propositional logic, more recently revived and augmented by G. Spencer Brown in his *Laws of Form*. What I contributed to their development was an extension from tree-like forms to what graph theorists know as cacti, and thereby hangs many a tale yet to be told. I hope to add more proof animations as time goes on.

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