 There are at least three serious questions about Aristotle’s substantial forms. One we have already noticed, namely (i) whether such forms are universals or particulars. The others are (ii) what is the relationship between the substantial form and the properties that enter into its definition? We have already noticed this question when discussing Categories. (iii) What is the ontological status of such forms? This is connected with the second question, for it is connected with the question of what the substantial form is over and above the properties essential to it. What I mean by this is as follows. Let us agree, for purposes of argument, that human being is a kind of substance and that rationality and animality are the properties in terms of which that substance is defined. It is uncontroversial that these properties are meant to be objective features of the external world. But what is the relation between the substantial form and those properties? Is the presence of the substantial form human being nothing more than the presence of those properties, or is the form something further that is, in some sense responsible for the presence of those properties? We saw in the previous section that the differentia in terms of which a substance is defined is not treated as being ‘in’ objects, as other properties are. This seems to suggest that calling an object a substance of a certain sort is not just a way of attributing to it the properties in terms of which it is defined. Aristotle is undoubtedly a realist about substantial forms, in the sense of thinking them to be something more than a mere collection of properties, but how are we to understand this ‘more’?