It is important to note that, in Parts 3 through 4 of the "Ethics", Spinoza describes how the human mind is affected by both mental and physical factors. He directly contests and denies dualism. Spinoza's main contention with Cartesian mind–body dualism was that, if mind and body were truly distinct, then it is not clear how they can coordinate in any manner. Humans presume themselves to have free will, he argues, which is a result of their awareness of appetites that affect their minds, while being unable to understand the reasons why they desire what they desire and act as they do. The universal Substance emanates both body and mind; while they are different attributes, there is no fundamental difference between these aspects. This formulation is a historically significant solution to the mind–body problem known as neutral monism. Spinoza's system also envisages a God that does not rule over the universe by Providence, by which it can and does make changes, but a God that is the deterministic system of which everything in nature is a part. Spinoza argues that "things could not have been produced by God in any other way or in any other order than is the case"; he directly challenges a transcendental God that actively responds to events in the universe. Everything that has and will happen is a part of a long chain of cause-and-effect, which, at a metaphysical level, humans are unable to change. No amount of prayer or ritual will sway God. Only knowledge of God provides the best response to the world around them. Not only is it impossible for two infinite Substances to exist (two infinities being absurd), God as the ultimate Substance cannot be affected by anything else, or else it would be affected by something else, and not be the fundamental, all-pervasive Substance.