We have just seen Lange's thorough criticism of Wolffian philosophy leading to the surprising conclusion that Wolff was no better than a common atheist like Spinoza was thought to be. By coincidence, Wolff had the very same year written a treatise – De differentia nexus rerum sapientis, nec non systematis harmoniae praestabilitae et hypothesium Spinosae luculenta commentatio, in qua simul genuina Dei existantiam demonstrandi ratio expenditur et multa religionis naturalis capita illustrantur – where he explicitly tried to show how the Leibnizian tradition differed from Spinozism.
As the title so clearly says, Wolff tried to establish two points of difference: one concerned the supposed necessity of the world, while the issue of second was the interaction of souls and bodies. Of these two points, the second is easier to decide. True, it appears that Wolff and Spinoza have identical views of the topic: both deny any true interaction of souls and bodies and maintain that the series of bodily changes and the series of mental states should somehow reflect one another. Yet, there is a crucial difference. Leibniz and Wolff envisioned the body and the soul as two different substances, while Spinoza thought them to be mere aspects of one human being. With Spinoza then, as Wolff's student Bilfinger had already pointed out, bodies and souls were necessarily intertwined. Wolff and Leibniz, on the contrary, accept that the union of the two substances is contingent and therefore separable. This is important especially as a justification of the Christian notion of life after death – soul or consciousness might exist also without any body to sustain it.
A more interesting questions concern the difference between a fatalistic world of Spinoza and a world created by a wise God. At first sight it appears quite incomprehensible how one could even confuse the two. After all, Spinoza's world is necessary and only that is possible what happens within that world – there is then nothing truly contingent, because all things follow necessarily from the very necessity of God and therefore only a person with inadequate information could call things contingent. Wolffian God, on the other hand, can think of true alternative possibilities and chooses one of them as the world to be created. Hence, even if the laws of Wolff's actual world are just as unbreakable as in Spinoza's necessary world, these laws are still contingent according to a more extensive perspective – God could have chosen other laws.
But as we saw from Lange's criticism, the true problem lies in Wolff's notion of God. Wolff emphasizes the understanding of God, when he describes God as a wise and intelligent creator. But understanding is a passive capacity – when God sees that a certain possible world is the most optimal, he cannot decide himself what to describe as the best possible world. Thus, because God is also good and he must automatically choose to create the best possible world, it appears that we could replace God with a very powerful computer that would just have enough capacity for viewing even the smallest details of all possible worlds.
Wolff's answer is to suggest that his opponents fall into equally ridiculous consequences and are even closer to outright Spinozism. Wolff's point is that if his opponents wish to de-emphasize the omniscience of God's understanding, they must at the same time emphasize the omnipotence of his will, that is, they must hold that divine will has a power to do things that the divine understanding has not decreed to be good. Now creation becomes a blind act of will – God becomes like an unstoppable and irrational manufacturing plant that just spurts out things without any rhyme or reason. Sure, what is produced is in a sense contingent, but because of the omnipotency of creator, the world feels like it is governed by a rigid necessity – and this time there's not even the justification that this is all for the best.
The struggle between Wolff and his supposed opponents circles then around the question whether the freedom of God, and indeed, any conscious being, falls more to his will or to his understanding. In a sense, it is quite obvious that it is our capacity to choose that makes us free – if we could just watch what happens, without having the ability to affect anything, we would not be truly free. Yet, as Wolff among other philosophers has pointed out, mere blind will without understanding is equally not free – after all, we wouldn't call a machine that works on randomly generated numbers a free person. It appears then that both understanding and will are required for the possibility of truly free decisions; I shall not pursue the question how to unify the two faculties into a coherent whole.
So much for the question of necessity. Next, we'll have a short detour on Chinese philosophy.