We define the term ⌜\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\ulcorner $$\end{document}a set T of sentential-logical formulae grounds a sentential-logical formula A from a syntactic point of view⌝\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\urcorner $$\end{document} in such a way that A is a syntactic sentential-logical consequence of T, and specific additional syntactic requirements regarding T and A are fulfilled. These additional requirements are developed strictly within the syntactics of sentential-logical languages, the three most important (...) being new, namely: to be atomically minimal, to be minimal in degree, and not to be conjunction-like. Our approach is independent of any specific sentential-logical calculus. (shrink)

In this article we prove step by step the main theorem of Smullyan sets. This main theorem says that each element of a Smullyan set is simultaneously satisfiable in a semantic system of model sets and therefore also, for example, in a semantic system of truth sets as well as in a semantic system according to Henkin. After that, we prove the semantical compactness of a propositional logic system as an example of a utilisation of Smullyan sets and its main (...) theorem. (shrink)

In this article we prove step by step the main theorem of Smullyan sets. This main theorem says that each element of a Smullyan set is simultaneously satisfiable in a semantic system of model sets and therefore also, for example, in a semantic system of truth sets as well as in a semantic system according to Henkin. After that, we prove the semantical compactness of a propositional logic system as an example of a utilisation of Smullyan sets and its main (...) theorem. (shrink)

In this article we compare three different semantic theories for a propositional language, namely a valuation-semantic, a truth-set- semantic and a modal-set-semantic theory. We prove step by step that these semantic theories are mutually equivalent.

In this article we compare three different semantic theories for a propositional language, namely a valuation-semantic, a truth-set- semantic and a modal-set-semantic theory. We prove step by step that these semantic theories are mutually equivalent.

We define the term \a set T of sentential-logical formulae grounds a sentential-logical formula A from a syntactic point of view\ in such a way that A is a syntactic sentential-logical consequence of T, and specific additional syntactic requirements regarding T and A are fulfilled. These additional requirements are developed strictly within the syntactics of sentential-logical languages, the three most important being new, namely: to be atomically minimal, to be minimal in degree, and not to be conjunction-like. Our approach is (...) independent of any specific sentential-logical calculus. (shrink)