6. There is a certain power in us which rules over physical organs, corrects sense-errors, and unifies all knowledge. This unifying principle which reflects over the material brought before it through the sense-channel, and, weighing the evidence of each sense, decides the character of rival statements, must itself stand above the sphere of matter. The combined force of these considerations, says Ibn Maskawaih, conclusively establishes the truth of the proposition--that the soul is essentially immaterial. The immateriality of the soul signifies its immortality; since mortality is a characteristic of the material. § II. Avicenna (d. 1037). Among the early Persian Philosophers, Avicenna alone attempted to construct his own system of thought. His work, called "Eastern Philosophy" is still extant; and there has also come down to us a fragment[38:1] in which the Philosopher has expressed his views on the universal operation of the force of love in nature. It is something like the contour of a system, and it is quite probable that ideas expressed therein were afterwards fully worked out. [38:1] This fragment on love is preserved in the collected works of Avicenna in the British Museum Library and has been edited by N. A. F. Mehren. (Leiden, 1894.) Avicenna defines "Love" as the appreciation of Beauty; and from the standpoint of this definition he explains that there are three categories of being:-- 1. Things that are at the highest point of perfection. 2. Things that are at the lowest point of perfection. 3. Things that stand between the two poles of perfection. But the third category has no real existence; since there are things that have already attained the acme of perfection, and there are others still progressing towards perfection. This striving for the ideal is love's movement towards beauty which, according to Avicenna, is identical with perfection. Beneath the visible evolution of forms is the force of love which actualises all striving, movement, progress. Things are so constituted that they hate non-existence, and love the joy of individuality in various forms. The indeterminate matter, dead in itself, assumes, or more properly, is made to assume by the inner force of love, various forms, and rises higher and higher in the scale of beauty. The operation of this ultimate force, in the physical plane, can be thus indicated:-- 1. Inanimate objects are combinations of form, matter and quality. Owing to the working of this mysterious power, quality sticks to its subject or substance; and form embraces indeterminate matter which, impelled by the mighty force of love, rises from form to form. 2. The tendency of the force of love is to centralise itself. In the vegetable kingdom it attains a higher degree of unity or centralisation; though the soul still lacks that unity of action which it attains afterwards. The processes of the vegetative soul are:-- (a) Assimilation. (b) Growth. (c) Reproduction.