The teleological quality of behaviour becomes impossible to deny when it is consciously pursued, for we know from direct experience that we often do have a preconceived image of a desired end state to which we strive. When we enter the realm of conscious experience, we again cross a threshold of organizational complexity that throws up its own new concepts thoughts, feelings, hopes, fears, memories, plans, volitions. A major problem is to understand how these mental events are consistent with the laws and principles of the physical universe that produces them.
The reductionist is here presented with a severe difficulty. If neural processes are nothing but the motions of atoms and electrons slavishly obeying the laws of physics, then mental events must be denied any distinctive reality altogether, for the reductionist draws no fundamental distinction between the physics of atoms and electrons in the brain and the physics of atoms and electrons elsewhere. This certainly solves the problem of the consistency between the mental and physical world.
However, one problem is solved only to create another. If mental events are denied reality, reducing humans to mere automata, then the very reasoning processes whereby the reductionists position is expounded are also denied reality. The argument therefore collapses amid its own self-reference.
On the other hand, the assumption that mental events are real is not without difficulty. If mental events are in some way produced by physical processes such as neural activity, can they possess their own independent dynamics?
The difficulty is most acutely encountered in connection with volition, which is perhaps the most familiar example of downward causation. If I decide to lift my arm, and my arm subsequently rises, it is natural for me to suppose that my will has caused the movement. Of course, my mind does not act on my arm directly, but through the intermediary of my brain. Evidently the act of my willing my arm to move is associated with a change in the neural activity of my brain certain neurons are triggered and so forth which sets up a chain of signals that travel to my arm muscles and bring about the required movement.
There is no doubt that this phenomenon part of what is known as the mind-body problem presents the greatest difficulty for science. On the one hand, neural activity in the brain is supposed to be determined by the laws of physics, as is the case with any electrical network. On the other hand, direct experience encourages us to believe that, at least in the case of intended action, that action is caused by our mental states. How can one set of events have two causes?
Undoubtedly relevant to this issue is the fact that the brain is a highly nonlinear system and so subject to chaotic behaviour. The fundamental unpredictability of chaotic systems and their extreme sensitivity to initial conditions endows them with an open, whimsical quality. Physicist James Crutchfield and his colleagues believe that chaos provides for free will in an apparently deterministic universe:
"Innate creativity may have an underlying chaotic process that selectively amplifies small fluctuations and molds them into macroscopic coherent mental states that are experienced as thoughts. In some cases the thoughts may be decisions, or what are perceived to be the exercise of will. In this light, chaos provides a mechanism that allows for free will within a world governed by deterministic laws."