There is no question that we live in a deterministic universe.  Despite some of the uncertainties and probabilities that are exhibited in the quantum world, the world we actually deal with is functionally deterministic.  While we may encounter unpredictable events, they are not random in the sense that they are without cause, or indeterminate.

In fact, part of the problem in considering free will, is the idea that knowledge isn't possible without determinism, since the presumption is that past knowledge or experience can be applied to future events with consistency.  The entire scientific method is based on predictability which necessitates determinism¹.

Even the issues with chaotic systems still presumes determinism, albeit with the restriction that without absolute knowledge of initial conditions then accurate predictability is impossible.  

Therefore we must conclude that our brains are also subject to determinism which is cerainly easy to see when examining the physiology of the system.  Neurons have specific functions, and brain chemistry plays a role, but regardless of the circumstances that trigger any given activity, there is a clearly deterministic result which is expected.  In addition, these higher order structures are determined by our genetics, which further closes the possibility of having extraneous influences that could be considered as operating "freely".

When we extend this perspective into the psychology of the mind, we also expect determinism to be in force since every action taken by an individual is precipitated by a particular cause.  There is never any situation where there is absolutely no explanation or cause for a given behavior.  In fact, when a behavior seems inexplicable we may well postulate that there is something wrong with the underlying brain physiology rather than suggest that it was simply indeterminant or random.

Note that we are neglecting the effects of learning or indoctrination at this point and concentrating solely on the mechanistic aspects of the brain.

As a result, we are forced into the situation of acknowledging that the basic operation of our brains, as well as the world around us are all explainable from the perspective of definitive causes leading to their corresponding effects.  In short, a world largely governed by determinism.

In the next article, we will consider the role of indoctrination and training and the effect it has on this deterministic system.

¹Once again, I will neglect the probabilistic situation of the sub-atomic environment since that doesn't appear to translate into the macro world experience.