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Logic and Ontology (Stanford Encyclopedia of Philosophy)
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Logic and Ontology<br>First published Mon Oct 4, 2004; substantive revision Mon Mar 13, 2023
A number of important philosophical problems are at the intersection<br>of logic and ontology. Both logic and ontology are diverse fields<br>within philosophy and, partly because of this, there is not one single<br>philosophical problem about the relation between them. In this survey<br>article we will first discuss what different philosophical projects<br>are carried out under the headings of “logic” and<br>“ontology” and then we will look at several areas where<br>logic and ontology overlap.
1. Introduction
2. Logic
2.1 Different conceptions of logic
2.2 How the different conceptions of logic are related to each other
3. Ontology
3.1 Different conceptions of ontology
3.2 How the different conceptions of ontology are related to each other
4. Areas of overlap
4.1 Formal languages and ontological commitment. (L1) meets (O1) and (O4)
4.2 Is logic neutral about what there is? (L2) meets (O2)
4.3 Formal ontology. (L1) meets (O2) and (O3)
4.4 Carnap’s rejection of ontology. (L1) meets (O4) and (the end of?) (O2)
4.5 The fundamental language. (L1) meets (O4) and (the new beginning of?) (O2)
4.6 The form of thought and the structure of reality. (L4) meets (O3)
5. Conclusion
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1. Introduction
Both logic and ontology are important areas of philosophy covering<br>large, diverse, and active research projects. These two areas overlap<br>from time to time and problems or questions arise that concern both.<br>This survey article is intended to discuss some of these areas of<br>overlap. In particular, there is no single philosophical problem of<br>the intersection of logic and ontology. This is partly so because the<br>philosophical disciplines of logic and of ontology are themselves<br>quite diverse and there is thus the possibility of many points of<br>intersection. In the following we will first distinguish different<br>philosophical projects that are covered under the terms<br>‘logic’ and ‘ontology’. We will then discuss a<br>selection of problems that arise in the different areas of<br>contact.
‘Logic’ and ‘ontology’ are big words in<br>philosophy, and different philosophers have used them in different<br>ways. Depending on what these philosophers mean by these words, and,<br>of course, depending on the philosopher’s views, sometimes there<br>are striking claims to be found in the philosophical literature about<br>their relationship. But when Hegel, for example, uses<br>‘logic’, or better ‘Logik’, he means something<br>quite different than what is meant by the word in much of the<br>contemporary philosophical scene. We will not attempt to survey the<br>history of the different conceptions of logic and of ontology, nor the<br>history of the debate about their relationship. Instead this article<br>will look at this issue fairly top down, with an emphasis on areas of<br>overlap that are presently actively debated. For more historical<br>information, see Kneale and Kneale 1985. Nonetheless, two<br>historically important figures, namely Gottlob Frege and Immanuel<br>Kant, will make repeat appearances below.
2. Logic
There are several quite different topics put under the heading of<br>‘logic’ in contemporary philosophy, and it is<br>controversial how they relate to each other.
2.1 Different conceptions of logic
On the one hand, logic is the study of certain mathematical properties<br>of artificial, formal languages. It is concerned with such languages<br>as the first or second order predicate calculus, modal logics, the<br>lambda calculus, categorial grammars, and so forth. The mathematical<br>properties of these languages are studied in such subdisciplines of<br>logic as proof theory or model theory. Much of the work done in this<br>area these days is mathematically difficult, and it might not be<br>immediately obvious why this is considered a part of philosophy.<br>However, logic in this sense arose from within philosophy and the<br>foundations of mathematics, and it is often seen as being of<br>philosophical relevance, in particular in the philosophy of<br>mathematics, and in its application to natural languages.
A second discipline, also called ‘logic’, deals with<br>certain valid inferences and good reasoning connected to them. The<br>idea here is that there are certain patterns of valid inferences which<br>are both an object of study...