11. Ideas of substances, being got only by collecting their qualities, are all inadequate.
So that all our complex
ideas of substances are imperfect and inadequate. Which would be so also in mathematical figures, if we were to
have our complex ideas of them, only by collecting their properties in reference to other figures. How uncertain
and imperfect would our ideas be of an ellipsis, if we had no other idea of it, but some few of its properties?
Whereas, having in our plain idea the whole essence of that figure, we from thence discover those properties, and
demonstratively see how they flow, and are inseparable from it.
