This external world is but the gross form of the internal, or subtle. The finer is always the cause and the grosser the effect. So the external world is the effect, and the internal the cause. In the same way external forces are simply the grosser parts, of which the internal forces are the finer. One who has discovered and learned how to manipulate the internal forces will get the whole of nature under his control… He will be master of the whole of nature, internal and external.