The Alchemist realizes that he himself is the Philosopher's Stone, and that this stone becomes like a diamond when salt and sulfur, or spirit and body, are united through mercury, the bond of the mind.

Man is the embodied principle of the mind, just as the animal is that of emotion.

He stands with one foot in heaven and the other on earth. His higher self rises to the “celestial” spheres, but the lower man ties him to matter. Now the philosopher, in building its sacred stone, it does so by harmonizing its spirit and its body. The result is the Philosopher's Stone. The harsh blows of life gradually peel and carve it until it reflects light from a million different angles.

— Manly P. Hall (The Initiates of the Flame).