Webster's Revised Unabridged Dictionary · 1913

Psychology

Psychology , noun

[Psycho- + -logy: compare French psychologie. See Psychical.]

The science of the human soul; specifically, the systematic or scientific knowledge of the powers and functions of the human soul, so far as they are known by consciousness; a treatise on the human soul.
Psychology, the science conversant about the phenomena of the mind, or conscious subject, or self. — Sir W. Hamilton