Ernest Holmes said this quote

The principle of any science is invisible, theoretical, as is our idea of Spirit. No one has seen God; no one has seen Life; what we have seen is the manifestation of Life. No one has seen Intelligence; we experience it. No one has ever seen Causation; we can see what It does, we deal with Its effects. We do not see Beauty. The artist feels beauty and depicts it as best he can, and the result of his effort is what we call the beautiful...We do not see Life, we experience living. Causation is invisible.