Abdu’l-Baha has expressed this conception of the nature of knowledge in the following terms: Reflect that man’s power of thought consists of two kinds. One kind is true, when it agrees with a determined “reality.” Such conceptions find realization in the exterior world; such are accurate opinions, correct theories, scientific discoveries and inventions. The other kind of conceptions is made up of vain thoughts and useless ideas which yield neither fruit nor result, and which have no reality. No, they surge like the waves of the sea of imaginations, and they pass away like idle dreams. Let us sum up briefly. A human idea is a subjective mental entity by its very nature. Some ideas are vain in that they do not correspond to any reality outside of themselves. Other ideas are true in that they reflect or mirror some configuration in reality via an appropriate correspondence between themselves.
A Logical Proof of the Existence of God – By William Hatcher.
Minimalism – A Book by William Hatcher.