It is evident too that if some perception is wanting, it is necessary for some understanding to be wanting too which it is impossible to get if we learn either by induction or by demonstration, and demonstration depends on universals and induction on particulars, and it is impossible to consider universals except through induction (since even in the case of what are called abstractions one will be able to make familiar through induction that some things belong to each genus, even if they are not separable, in so far as each thing is such and such), and it is impossible to get an induction without perception for of particulars there is perception; for it is not possible to get understanding of them; for it can be got neither from universals without induction nor through induction without perception.