In Consilience: The Unity of Knowledge, E.O. Wilson writes:
Without the stimulus and guidance of emotion, rational thought slows and disintegrates. The rational mind does not float above the irrational. It cannot free itself to engage in pure reason. There are pure theorems in mathematics, but no pure thoughts that discover them. In the brain-in-the-vat fantasy of neurobiological theory and science fiction, the organ in its nutrient bath has been detached from the impediments of the body, and liberated to explore the inner universe of the mind. But that is not what would ensue in reality. All the evidence from the brain sciences points in the opposite direction, to a waiting coffin-bound hell of the wakened dead, where the remembered and imagined world decays until chaos mercifully grants oblivion.
Consciousness satisfies emotion by the physical actions it selects in the midst of turbulent sensation. It is the specialized part of the mind that creates and sorts scenarios, the means by which the future is guessed, and courses of action chosen. Consciousness is not a remote command center, but part of the system, intimately wired to all the neural and hormonal circuits regulating physiology. Consciousness acts and reacts to achieve a dynamic steady state. It perturbs the body in precise ways with each changing circumstance, as required for well-being and response to opportunity, and helps return it to the original condition when challenge and opportunity have been met.
The reciprocity of mind and body can be visualized in the following scenario which I have adopted from an account by the neurologist Antonio R. Dimasio. Imagine that you are strolling along a deserted city street at night. Your revery is interrupted by quick footsteps drawing close behind. Your brain focuses instantly and churns out alternative scenarios: ignore, freeze, turn and confront, or escape. The last scenario prevails, and you act. You run toward a lighted storefront further down the street. In the space of a few seconds, the conscious response triggers automatic changes in your physiology. The catecholenine hormones epinephrine, adrenaline, and norepinephrine pour into the blood stream from the adrenal medulla and travel to all parts of the body, increasing the basal metabolic rate, breaking down glycogen in the liver and skeletal muscles to glucose for a quick energy feed. The heart races, the bronchials of the lungs dilate to admit more air, digestion slows, the bladder and colon prepare to void their contents, disencumbering the body to prepare for violent action and possible injury.
A few seconds more pass, time slows in the crisis, the event span seems like minutes. Signals arising from all the changes are relayed back to the brain by more nerve fibers and the rise of hormone titres in the blood stream. As further seconds tick away, the body and brain shift together in precisely programmed ways. Emotional circuits of the lambic system kick in. The new scenarios flooding the mind are charged with fright, then anger, that sharply focuses the attention of the cerebral cortex, closing out almost all other thought not relevant to immediate survival.
The storefront is reached, the race won. People are inside. The pursuer is gone. Was the follower really in pursuit? No matter. The republic of bodily systems informed by reassuring signals from the conscious brain begins its slow stand down to the original calm state.
Dimasio, in depicting the mind holistically in such episodes, has suggested the existence of two broad categories of emotion
The first, primary emotion, comprises the responses ordinarily called inborn, or instinctive. Primary emotion requires little consciousness activity beyond the recognition of certain elementary stimuli, the kind that students of instinctive behavior in animals call releasers.
Secondary emotions arise from personalized events of life. To meet an old friend, fall in love, win a promotion, or suffer an insult is to fire the limbic circuits of primary emotion, but only after the highest integrative processes of the cerebral cortex have been engaged. … Nature, Dimasio observes, “with its tinkerish knack for economy, did not select independent mechanisms for expressing primary and secondary emotions. It simply allowed secondary emotions to be expressed by the same channel already prepared to convey primary emotions.’“