them he is coming. If Jones doesn't go, then he ought not tell them he is coming. Jones doesn't go Jørgensen's dilemma Deontic logic faces Jørgensen's dilemma. This problem is best seen as a trilemma. The following three claims are incompatible: Logical inference requires that the elements (premises and conclusions) have truth-values Normative statements do not have truth-values There are logical inferences between normative statements Responses to this problem involve rejecting one of the three premises. The input/output logics reject the first premise. They provide inference mechanism on elements without presupposing that these elements have truth-values. Alternatively, one can deny the second premise. One way to do this is to distinguish between the norm itself and a proposition about the norm. According to this response, only the proposition about the norm (as is the case for Standard Deontic Logic) has a truth-value. For example, it may be hard to assign a truth-value to the argument "Take all the books off the table!", but ("take all the books off the table"), which means "It is obligatory to take all the books off the table", can be assigned a truth-value, because it is in the indicative mood. Finally, one can deny the third premise. But this is to deny that there is a logic of norms worth investigating. See also Deontological ethics Imperative logic Modal logic Moral reasoning Norm (philosophy) Free choice inference Notes Bibliography Lennart Åqvist, 1994, "Deontic Logic" in D. Gabbay and F. Guenthner, ed., Handbook of Philosophical Logic: Volume II Extensions of Classical Logic, Dordrecht: Kluwer. Dov Gabbay, John Horty, Xavier Parent et al. (eds.)2013, Handbook of Deontic Logic and Normative Systems, London: College Publications, 2013. Hilpinen, Risto, 2001, "Deontic Logic," in Goble, Lou, ed., The Blackwell Guide to Philosophical Logic. Oxford: Blackwell. External links Contrary-to-Duty Paradox, Internet Encyclopedia of Philosophy. Modal logic Philosophical logic