In his fragment on "Nafs" (soul) Avicenna endeavours to show that a material accompaniment is not necessary to the soul. It is not through the instrumentality of the body, or some power of the body, that the soul conceives or imagines; since if the soul necessarily requires a physical medium in conceiving other things, it must require a different body in order to conceive the body attached to itself. Moreover, the fact that the soul is immediately self conscious--conscious of itself through itself--conclusively shows that in its essence the soul is quite independent of any physical accompaniment. The doctrine of metempsychosis implies, also, individual pre-existence. But supposing that the soul did exist before the body, it must have existed either as one or as many. The multiplicity of bodies is due to the multiplicity of material forms, and does not indicate the multiplicity of souls. On the other hand, if it existed as one, the ignorance or knowledge of A must mean the ignorance or knowledge of B; since the soul is one in both. These categories, therefore, cannot be applied to the soul. The truth is, says Avicenna, that body and soul are contiguous to each other, but quite opposite in their respective essences. The disintegration of the body does not necessitate the annihilation of the soul. Dissolution or decay is a property of compounds, and not of simple, indivisible, ideal substances. Avicenna, then denies pre-existence, and endeavours to show the possibility of disembodied conscious life beyond the grave. We have run over the work of the early Persian Neo-Platonists among whom, as we have seen, Avicenna alone learned to think for himself. Of the generations of his disciples--Behmenyār, Ab u’l-Ma’mūm of Isfahān, Ma‘ṣūmī, Ab u’l-‘Abbās, Ibn Tāhir[44:1]--who carried on their master's Philosophy, we need not speak. So powerful was the spell of Avicenna's personality that, even long after it had been removed, any amplification or modification of his views was considered to be an unpardonable crime. The old Iranian idea of the dualism of Light and Darkness, does not act as a determining factor in the progress of Neo-Platonic ideas in Persia, which borrowed independent life for a time, and eventually merged their separate existence in the general current of Persian speculation. They are, therefore, connected with the course of indigenous thought only in so far as they contributed to the strength and expansion of that monistic tendency, which manifested itself early in the Church of Zoroaster; and, though for a time hindered by the Theological controversies of Islām, burst out with redoubled force in later times, to extend its titanic grasp to all the previous intellectual achievements of the land of its birth. [44:1] Al-Baihaqi; fol. 28a et seqq. CHAP. III. THE RISE AND FALL OF RATIONALISM IN ISLĀM. § I. The Metaphysics of Rationalism--Materialism.