Imperatives and logic

Imperatives and Logic Author(s): Jörgen Jörgensen Reviewed work(s): Source: Erkenntnis, 7.

J?rgen J?rgensen Imperatives and Logic: is to initiate a discussion of this communication (Copenhagen),

verb is in the imperative mood. Imperatives in this sense so comprise not only commands or orders but also requests, may pleas, appeals and other linguistic expressions of willing or wishingsomething to be done or not to be done, the differences between the main not being of a logical but of a expressions apparently are: "Be quiet", "Shut the door, character. Examples psychological be silly", "Do 3 by 5", "Don't your duty", please", "Multiply these "What you should not want done to yourself, do not do to others", "Act only on that maxim whereby thou canst at the same time will that itshould become a universal law".

on The object I the logical character of imperatives. By the word "imperative" sentences which I define as sentences inwhich understand imperative

Perhaps it will be expedient to start the discussion on the logical character of imperatives by stating the small puzzle that started the tentative reflections which
to you.

I will

now allow myself

tocommunicate

form it runs as follows: All cientific sentences are in the indicative mood, whereas all moral sentences are in the imperative mood. But from sentences in the indicative mood only sentences can be derived by logical are also in the indicative mood which it is impossible to infer a moral sentence from inference. Therefore centrated a scientific sentence, however much the concepts involvedmay be manipulated. The conclusiveness least mood I know

the famous argument by which Henri P o i n tried to demonstrate car? in his "Derni?res Pens?es" (p. 224?25) or ethics on science. In con? the impossibility of founding morals You all remember

neither of any

never be conclusive

take the word "inference" in the generally as e. g. by Professor Joseph accepted "a process of thoughtwhich, starting with one or more judgments, ends in another judgment whose truth is seen to be involved in that sense in which it is defined of the former" ("An Introduction it is clearly inplied to Logic", p. 232, Ocford 1931). that the conclusion of an inference will

nor of any a conclusion in the imperative mood from premisses in the indica? tive mood. And I think it can be proved that suchinferences can ifwe

of this argument I think we must admit. At scientific sentence in the imperative logical principles by which it is possible to derive

Here

Imperatives have to be a true judgment or

and Logic

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for the validity of an inference from a premiss p to a conclusion q, stating that the constitutive conditions are (1) p must be true, (2) p must imply q, whereas theepistemic conditions are (1) p must be known known to be true, (2) p must be known that q is true. to imply q without it being

is sentence, an implication which who (in her made still more conspicuous by Professor Stebbing "A modern Introduction to Logic", p. 215, London 1933) carefully distinguishes between the constitutive and the epistemic conditions

to this definition of a logical inferencea sentence in According cannot be inferred from sentences in the the imperative mood because indicative mood, the relation of implication only holds sentences which are capable of being either true or false between

(or at least of having one or the other values). But this condition imperative they can neither be true nor false in are used in logic. "Be quiet" ? words "Do your duty" meaninglessquestion. Unanswerable. accepted or The not

of two analoguous truth sentences do not fulfil, as any sense in which these ? is it true or false? A is it true or false?

justified; but to ask whether they are true or false seems without any sense as well as it seems impossible to indicate a method by to test their truth or falsehood. Therefore they are not

two commands may be obeyed or...