Again, you can have no real knowledge of nature, and its inward working power, but so far as the workings of nature, and the birth of things, are a working and birth in yourself. Natural reason may trade in the outside of things; it may measure, and make drafts of magnitude, height, and distance of things on the earth, and above the earth; it may make many and fine experiments of the powers of every element: but then this is going no farther into the ground of nature, than when the potter makes curious vessels with his clay and fire.