S there any reason to think that conjunctions of properties are themselves properties? Professor D. M. Armstrong has recently argued that there is ('Towards a Theory of Properties: Work in Progress on the Problem of Universals', Philosophy LII (I975), 144-5 5). Armstrong presents a theory of properties (p. 149) which is both 'Scientific Realist' ('what is a genuine property is to be decided by scientific investigation') and 'Aristotelian' ('we must reject the view that there are any uninstantiated properties'). Such a view, he claims, requires 'admitting conjunctive properties', by which he means accepting the following principle (cf. p. 153):