The secrets of his mental nature and the principles of intellectual life became at this stage gradually unfolded to his view. You will thus perceive, Brethren, that the F.C. degree, sometimes regarded by us as a somewhat uninteresting one, typifies in reality a long course of personal development requiring the most profound knowledge of the mental and psychical side of our nature. It involves not merely the cleansing and control of the mind, but a full comprehension of our inner constitution, of the more hidden mysteries of our nature and of spiritual psychology.
W L Wilmshurst, The Meaning of Masonry, Chapter I The Deeper Symbolism of Freemasonry