ABSTRACT
'Entailment' as a technical term in logic and philosophy was first introduced by Moore in the paper on 'External and Internal Relations'. Russell and C. I. Lewis and others had used the term 'implication' to mean what Moore called 'entailment'. It would seem that entailment relations can be properly said to hold also between other logical entities beside propositions. The 'possibility' of entailment relations between commands and norms constitutes a difficult and interesting problem. Entailment between commands and norms may be accounted for in terms of entailment between true-false propositions. Lewis, who suggested that entailment and strict implication are the same, must also be credited with the discovery of the so-called Paradoxes of Strict Implication. The failure of the attempt to give an account of entailment in terms of either material or strict implication consists, above all, in the fact that a relation of material or strict implication may subsist by virtue solely of the truth.
