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Organon F

Volume 27, May 2020, Issue 2, Pages 187–262

ISSN 2585-7150 (online) ISSN 1335-0668 (print)

Research Article

Boulesic Logic, Deontic Logic and the Structure of a Perfectly Rational Will

Daniel Rönnedal



In this paper, I will discuss boulesic and deontic logic and the relationship between these branches of logic. By ‘boulesic logic,’ or ‘the logic of the will,’ I mean a new kind of logic that deals with ‘boulesic’ concepts, expressions, sentences, arguments and systems. I will concentrate on two types of boulesic expression: ‘individual x wants it to be the case that’ and ‘individual x accepts that it is the case that.’ These expressions will be symbolised by two sentential operators that take individuals and sentences as arguments and give sentences as values. Deontic logic is a relatively well-established branch of logic. It deals with normative concepts, sentences, arguments and systems. In this paper, I will show how deontic logic can be grounded in boulesic logic. I will develop a set of semantic tableau systems that include boulesic and alethic operators, possibilist quantifiers and the identity predicate; I will then show how these systems can be augmented by a set of deontic operators. I use a kind of possible world semantics to explain the intended meaning of our formal systems. Intuitively, we can think of our semantics as a description of the structure of a perfectly rational will. I mention some interesting theorems that can be proved in our systems, including some versions of the so-called hypothetical imperative. Finally, I show that all systems that are described in this paper are sound and complete with respect to their semantics.


Boulesic logic; deontic logic; modal logic; practical rationality; the hypothetical imperative; the logic of the will; semantic tableaux.

Author(s) and affiliation(s)


Daniel Rönnedal


Stockholm University


Department of Philosophy, Stockholm University, Universitetsvägen 10 D, 106 91 Stockholm, Sweden



About this article


22 January 2019


4 November 2019

Published online

13 December 2019


Institute of Philosophy of the Slovak Academy of Sciences

Institute of Philosophy of the Czech Academy of Sciences

Cite as


Rönnedal, D. (2020). Boulesic Logic, Deontic Logic and the Structure of a Perfectly Rational Will. Organon F27(2), 187–262. https://doi.org/10.31577/orgf.2020.27203


Rönnedal, Daniel. 2020. "Boulesic Logic, Deontic Logic and the Structure of a Perfectly Rational Will." Organon F 27 (2): 187–262. https://doi.org/10.31577/orgf.2020.27203


Rönnedal, D. (2020). Boulesic Logic, Deontic Logic and the Structure of a Perfectly Rational Will. Organon F, 27(2), pp. 187–262. https://doi.org/10.31577/orgf.2020.27203

Copyright information

© Daniel Rönnedal

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