Semantic consistency is arbitrary and conventional while logical consistency is neither arbitrary nor conventional.

In logic, consistency refers to a system of axioms that does not contain any contradictions. A theory is consistent if it has a model, meaning that there exists an interpretation under which all of its axioms are true. In contrast, semantic consistency refers to the consistency of meaning or interpretation of a word or phrase. It is concerned with whether a word or phrase has a consistent meaning across different contexts. For example, if a word has different meanings in different contexts, it is semantically inconsistent.

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The inconsistency of meaning of a word or term primarily falls within logic rather than semantics. In Aristotelian logic, the inconsistency in the meanings of words or terms renders the argument invalid. Within semantics, the same may still be viewed as inconsistent but it is viewed as such not from the arbitrary and conventional point of view of semantics, but of logic.

Philadelphia, PA

Dear Benitez & readers,

The concept of semantic consistency/inconsistency is standardly used to to define the deductive validity of arguments. A set of statements is semantically inconsistent, iff there is no assignment of truth-values to the component statements on which they all turn out true. Notice that "true" and "interpretation" (as in "assignment of truth values") are both semantic concepts in theory of referential concepts.

In these terms, an argument, A1, A2, A3, . . . . An/ therefore B, is logically valid just in case the set of statements [A1, A2, A3, . . . An, not-B] is semantically inconsistent. This corresponds to the syntactic concept of proof and syntactically defined rules of inference that are employed to show that an argument is deductively valid. The semantic concept of deductive validity tells us what we aim for in a set of (syntactic) rules of inference.

It is in semantic terms that we understand how it is that deductively valid forms of argument are able to preserve truth, i.e., show that --if-- the premises are true, then the conclusion, follows, i.e., is also true.

You wrote:

Semantic consistency is arbitrary and conventional while logical consistency is neither arbitrary nor conventional.

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Here you seem to make use of an old-fashioned notion of semantics. But in logical theory the non-arbitrary concept of semantic consistency/ inconsistency is central. In identifying valid argument forms, the constant assumption is that for every linguistic expression, "E," and every occurrence of "E," "E" translates (has the same meaning as) "E."

Consider the following argument:

John put his money in a bank.

A bank is the side of a river.

Therefore, John put his money in the side of a river.

Though the form of argument is valid, something obviously goes wrong here, since there is an "arbitrary" variation in the meaning and interpretation of the word "bank."

On the other hand, sameness of reference is not alone sufficient for deductive validity of arguments, though sameness of reference is a condition of sameness of meaning.

In consequence, the following argument is deductively invalid:

John saw the evening star last night.

The morning star is in fact the brightest object in the sky this morning.

Therefore, John saw the in fact brightest object in the morning sky.

Without adding (the apparently "suppressed premise, the es = the ms, the argument fails of deductive validity, because though, in fact es = ms, the two terms differ in meaning.

H.G. Callaway

Dear H.G. Callaway,

I agree with everything you said above. In Aristotelian logic, particularly., categorical syllogism, one of the rules states that there should three and only three terms, namely, the major term, the middle term, and the minor term, each of which is used twice. You are correct, each of these terms must have semantic consistency. But requirement for semantic consistency is dictated primarily by logic not by semantics.

Philadelphia, PA

Dear Benitez & readers,

Notice that "true" and "interpretation" (as in "assignment of truth values") are both semantic concepts in theory of referential concepts.

Rules of deductive inference (or logical inference), in contrast are "syntactic" --attending only to the physical shapes of expressions --not their meaning.

The acceptability of a set of rules for logical inference depends on their meeting semantic criteria. Specifically, they must never allow construction (by application of the rules) of a false conclusion out of true premises.

Much of this comes out in Alfred Tarski's theory of truth and satisfaction. See also W.V. Quine, "Notes on the Theory of Reference," in Quine 1953, From a Logical Point of View --and in the work of Donald Davidson.

H.G. Callaway

Logical consistency is exact, semantic is not.

Prof. Kallaway me segue no RGate, e eu a ele. Semântica teria mais a ver com pessoas se falando, semântica, a prática da fala, e Lógica tem a ver com filosofia da matematicidade, descartiana, com a verdade de dois mais dois é igual a quatro. Portanto, ter consistência semântica é falar e escrever bem, pragmaticamente, como o grupo quer que se fale, talvez, uma verdade, para aquele grupo.

MAS PARA O GRUPO DOS FILÓSOFOS LÕGICOS, a consistência lógica está acima da existência. Para mim, concordo com estes últimos.

Philadelphia, PA

Dear all,

A.V. Sales writes:

BUT FOR THE GROUP OF LOGICAL PHILOSOPHERS, logical consistency is above existence. For me, I agree with the latter.

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Well, on the contrary, it might be argued that Tarski's semantic conception of truth starts from Aristotle on truth. "To say of what is, that it is, or to say of what is not, that it is not, that is truth" (as I recall Aristotle's definition).

There can be no non-relational concept of truth. Truth and falsity always pertain to "what is said" and its relation to what there is to talk about. But this does not mean that "logical consistency" is "above existence."

What exists, i.e., what there is to talk about, does not require anyone having already talked about it. The topic of "existence and quantification" may be of interest here.

H.G. Callaway