## Abstract

Does logic describe something or not? If not, is it a normative or practical discipline? Is there a radical division between the practical or normative level and the theoretical or descriptive level? A discipline is theoretical, we may say, if its main propositions contain descriptive expressions, such as “is” or “have”, but no normative expressions, such as “ought”, “ought not” or “may”. A discipline is normative if its main propositions are of the form “it ought to be”. Theoretical propositions express what *is*, whereas practical propositions express what *should be*. So a theoretical discipline is descriptive and a normative discipline is prescriptive, but what does a theoretical discipline describe?

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