If all Souls are from one source how do they manifest such diverse tendencies? Is their Source divided against itself?

But let Error be scourged by the inquiries of Truth in order that its disciples also may be confounded when they are convicted (and made to see) how greatly they err. For if, as they say, all the Souls are from one Nature, and their Nature is pure and beautiful, how can there be found in them two tendencies which are divided against one another? For there are among the Souls some who err and some who do not err; some who sin, and some who are pronounced righteous; [P. 168.] some who love the Good, and some who hate it. Let them tell us, therefore, what is the cause of this division that the Souls are thus divided against one another so that they are [cxii] quite unlike, nor do they agree with the source from which they came. If their Essence is not like its Nature it is found that their source is divided against itself. And lo, in virtue of what it is, a great Evil dwells in it, and the perturbation in it cannot be purged away because it is an Essence of which, in virtue of what it is, the Foulness cannot be refined. Why then, O Mani, did not the Souls come from this Good Part to wage war with the Darkness, since before the war they had had a great war in their own Domain, inasmuch as their Essence was divided against itself?