Again, if the universal is not a thing apart from the particulars, and demonstration instils an opinion that that in virtue of which it demonstrates is some thing, and that this belongs as a sort of natural object among the things there are (e.g. a triangle apart from the individual triangles, and a figure apart from the individual figures and a number apart from the individual numbers), and a demonstration about something there is is better than one about something that is not, and one by which we will not be led into error is better than one by which we will be, and universal demonstration is of this type (for as they go on they prove as in the case of proportion, eg that whatever is of such a type neither line nor number nor solid nor plane but something apart from these will be proportional)