Towards a Theory of Meaningfulness and Truth: An Introduction to Variational Semantics
Dissertation, University of Colorado at Boulder (
1992)
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Abstract
We start with a nearly arbitrary standard classical first order "language" $C\sb{o},$ which is expanded to $C\sb{M,T}$ = "$C\sb{o}+M+T$", where for any variable x, M and T are unary formulas. We start also with a model ${\cal T}\sb{o},$ which together with $C\sb{o}$ represents a fixed non-problematic interpreted first order language. For each $\mu,\tau\subseteq U\sb{o},$ the universe of discourse for ${\cal T}\sb{o},$ the model ${\cal T}\sb{\mu,\tau}$ over $C\sb{M,T}$ is given so that its reduct to $C\sb{o}$ is just ${\cal T}\sb{o},$ and so that for any $C\sb{M,T}$-variable x, the set-extensions of M and T are $\mu$ and $\tau$ respectively. For each $C\sb{M,T}$-expression e, $\vec e$ is its distinctly chosen representative in $U\sb{o},$ and $\lbrack\!\lbrack e\rbrack\!\rbrack$ is a constant $C\sb{o}$-term which names $\vec e.$ ;The goal is to find $\mu\sb*$ and $\tau\sb*,$ such that $\mu\sb*$ and $\tau\sb*$ plausibly and "self-referentially" approximate meaningfulness and truth respectively for any interpreted language represented by ${\cal T}\sb{\mu\sb*,\tau\sb*},$ by satisfying at least the following conditions. ; $\tau\sb*\subseteq\mu\sb*,$ and for each $C\sb{M,T}$-sentence $\sigma$ such that ${\cal T}\sb{\mu\sb*,\tau\sb*}\models M\lbrack\!\lbrack\sigma\rbrack\!\rbrack,$ $$\eqalign{&\ {\cal T}\sb{\mu\sb*,\tau\sb*} \models\sigma\Longleftrightarrow{\cal T}\sb{\mu\sb*,\tau\sb*}\models T\lbrack\!\lbrack\sigma\rbrack\!\rbrack,\ {\rm and}\cr&\ {\cal T}\sb{\mu\sb*,\tau\sb*}\models T\lbrack\!\lbrack\sigma\\leftrightarrow T\lbrack\!\lbrack\sigma\rbrack\!\rbrack\rbrack\!\rbrack.\cr}$$ ; There is a class of expression representatives $\mu\sp{D}\subseteq\mu\sb*$ containing every $C\sb{o}$-expression representative, such that the set $\tau\sp{D}=\mu\sp{D}\ \cap\ \tau\sb*$ itself satisfies the following properties. ;First, for each $\vec\sigma$ such that $\sigma$ is a $C\sb{M,T}$-sentence, if for all $\mu,\tau\subseteq U\sb{o}$ satisfying $\mu\supseteq\mu\sb*$ and $\tau\supseteq\tau\sp{D},$ it is the case that ${\cal T}\sb{\mu,\tau}\models\sigma,$ then $\vec\sigma\in\tau\sp{D}.$ ;Second, whenever $\vec\sigma\in\tau\sp{D},$ then also $\sp{\vec{\enspace}}\ \in\tau\sp{D}.$ ;Third, $\tau\sp{D}$ is "upwardly closed" with respect to the strong-Kleene rules for the truth-value evaluation of Boolean combinations of formulas. For example, for $C\sb{M,T}$-sentences $e\sb1$ and $e\sb2$: $$\eqalign{&\ \vec e\sb1\in\tau\sp{D}\Longleftrightarrow)\sp{\vec{\enspace}}\ \in\tau\sp{D}.\cr&\ {\rm If}\ \vec e\sb1\in\tau\sp{D}\ {\rm or}\ \vec e\sb2\in\tau\sp{D},\ {\rm then\ so\ is}\ \sp{\vec{\enspace}}\ \in\tau\sp{D}.\cr&\ {\rm If}\ \sp{\vec{\enspace}}\ \in\tau\sp{D}\ {\rm and}\ \sp{\vec{\enspace}}\ \in\tau\sp{D},\ {\rm then}\ )\sp{\vec{\enspace}}\ \in\tau\sp{D}.\cr}$$ ; For each $C\sb{M,T}$-expression e not involving T, ${\cal T}\sb{\mu\sb*,\tau\sb*}\models M\lbrack\!\lbrack e\rbrack\!\rbrack$; in particular, for any $C\sb{M,T}$-expression e whatsoever, ${\cal T}\sb{\mu\sb*,\tau\sb*}\models M\lbrack\!\lbrack\\neg M\lbrack\!\lbrack e\rbrack\!\rbrack\rbrack\!\rbrack.$ ; ;In this dissertation, it is shown for the first time that there are in fact $\mu\sb*$ and $\tau\sb*$ which simultaneously satisfy all three conditions , , and , even when the consequent of the Godel fixed point theorem must hold