Concept
Deontic modality
Overview
Deontic modality (abbreviated deo) is a linguistic modality that indicates how the world ought to be according to certain norms, expectations, speaker desires, etc. In other words, a deontic expression indicates that the state of the world (where 'world' is loosely defined here in terms of the surrounding circumstances) does not meet some standard or ideal, whether that standard be social (such as laws), personal (desires), etc. The sentence containing the deontic modal generally indicates some action that would change the world so that it becomes closer to the standard or ideal.
This category includes the following subcategories:
Commissive modality (the speaker's commitment to do something, like a promise or threat; alethic logic or temporal logic would apply): "I shall help you."
Directive modality (commands, requests, etc.; deontic logic would apply): "Come!", "Let's go!", "You've got to taste this curry!"
Volitive modality (wishes, desires, etc.; boulomaic logic would apply): "If only I were rich!"
A related type of modality is dynamic modality, which indicates a subject's internal capabilities or willingness as opposed to external factors such as permission or orders given.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
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In their case, therefore, the moral law is an imperative, which commands categorically, because the law is unconditioned; the relation of such a will to this law is dependence under the name of obligation, which implies a constraint to an action, though only by reason and its objective law; and this action is called duty, because an elective will, subject to pathological affections (though not determined by them…
Immanuel Kant, The Critique of Practical Reason
States what Deontic modality is.
In the first case the action interests me; in the second the object of the action (because it is pleasant to me), We have seen in the first section that in an action done from duty we must look not to the interest in the object, but only to that in the action itself, and in its rational principle (viz. the law).]
Michel de Montaigne, Literary and Philosophical Essays
States what Deontic modality is.
Practical principles are formal when they abstract from all subjective ends; they are material when they assume these, and therefore particular springs of action. The ends which a rational being proposes to himself at pleasure as effects of his actions (material ends) are all only relative, for it is only their relation to the particular desires of the subject that gives them their worth, which therefore cannot…
Immanuel Kant, Fundamental Principles of the Metaphysic of Morals
States what Deontic modality is.
Related ideas
Place in the tradition
Part of Deontic logic.