A human being is a combination of the dust of the earth and the breath of heaven. There is something spiritual and eternal about every person. Discussions of the soul and matters of the spirit are critical to understanding how we live and find meaning in life.
However, science has helped draw back the curtain on the human mind and how we think and conceive of the world, seen and unseen, around us. Brain scans, a major leap forward in brain study, help scientists see and chart the areas responsible for various thoughts, emotions, and actions. Essentially, the brain is a carefully tuned chemical and biological matrix of neurons and neurotransmitters generating electrical circuits that enable us to, among other things, read this sentence and remember it.
In addiction, two main neurotransmitters are in play: Dopamine and Glutamate.
Dopamine is the pleasure neurotransmitter. When an experience is pleasurable the midbrain releases dopamine initiating a cascade of responses that tell the brain "this is good and desirable." This is also called the pleasure circuit.
Glutamate is the memory neurotransmitter. When the midbrain releases dopamine it says "this is good, and I want it." The prefrontal cortex then releases glutamate to say "remember this and go get it."
Again when this delicate balance works properly it enables us to enjoy life appropriately. Our desires and instincts (from the midbrain) are necessary for survival and neutral in terms of morality. The prefrontal cortex enables us to seek and enjoy pleasures in a good, helpful, and balanced manner.
Addiction wrecks the balance.