In this connection Hādī approvingly quotes the poet Jāmī who has given the most beautiful poetic expression to Plato's Doctrine of Ideas in verses which can be thus translated:-- "The ideas are glasses of various colours in which the Sun of Reality reflects itself, and makes itself visible through them according as they are red, yellow or blue."[181:2] [178:2] Asrār al-Ḥikam; p. 8. [179:1] Asrār al-Ḥikam; p. 8. [179:2] Asrār al-Ḥikam; p. 10. [180:1] Asrār al-Ḥikam; pp. 28, 29. [181:1] Asrār al-Ḥikam; p. 151. [181:2] Asrār al-Ḥikam; p. 6. In his Psychology he mostly follows Avicenna, but his treatment of the subject is more thorough and systematic. He classifies the soul in the following manner:-- The Soul │ ┌─────────┴─────┐ │ │ Heavenly Earthly │ ┌────────┼──────────┐ │ │ │ Human Animal Vegetative Powers:-- 1. Preserving the individual. 2. Perfecting the individual. 3. Perpetuating the species. The animal soul has three powers:-- 1. External senses┐ Perception. 2. Internal senses┘ 3. Power of motion which includes. (a) Voluntary motion. (b) Involuntary motion. The external senses are taste, touch, smell, hearing and sight. The sound exists outside the ear, and not inside as some thinkers have held. For if it does not exist outside the ear, it is not possible to perceive its direction and distance. Hearing and sight are superior to other senses, and sight is superior to hearing; since:-- I. The eye can perceive distant things. II. Its perception is light, which is the best of all attributes. III. The construction of the eye is more complicated and delicate than that of the ear. IV. The perceptions of sight are things which actually exist, while those of hearing resemble non-existence. The internal senses are as follow:-- (1). The Common Sense--the tablet of the mind. It is like the Prime Minister of the mind sending out five spies (external senses) to bring in news from the external world. When we say "this white thing is sweet", we perceive whiteness and sweetness by sight and taste respectively, but that both the attributes exist in the same thing is decided by the Common Sense. The line made by a falling drop, so far as the eye is concerned, is nothing but the drop. But what is the line which we see? To account for such a phenomenon, says Hādī, it is necessary to postulate another sense which perceives the lengthening of the falling drop into a line.