1.2 The Puzzle of Consciousness

summary

Science has yet to explain how the brain gives rise to the mind.

Science has allowed us to understand many physical aspects of the universe extraordinarily well, from the large-scale structure of the cosmos to the microscopic processes of chemistry and biology. Yet nowhere in these fields of knowledge is there any description of how consciousness arises.
There are some philosophers who reject the notion that consciousness depends on physics at all, often using the zombie argument, which states that we can imagine a world that is fully compatible with the laws of nature and in which consciousness is absent.
Gottfried Wilhelm Leibniz discussed the difficulty of solving this problem in his 1714 work La Monadologie. He argued that if we could enlarge a brain and inspect it, we “will only find parts that push one another, and we will never find anything to explain a perception.”
Today this is known as the hard problem of consciousness, a term introduced by philosopher David Chalmers. It refers to the problem of explaining how and why the physical processes of the brain result in subjective conscious experiences.

'I think therefore I am.'

This phrase originally appeared in French as je pense, donc je suis in Rene Descartes’ Discours de la méthode. It is famously translated to Latin as cogito, ergo sum.
Cartesian doubt is a method of systematic skepticism about the truths of one’s beliefs that was popularized by Descartes. He reasoned that the only truth that he was absolutely certain of was his existence, because he felt conscious. Essentially, there has to be a thinking entity in order for there to be a thought. All other understanding comes second to this fundamental observation, as consciousness is the only thing we have direct acquaintance with.
Other knowledge could be distorted by imagination, deception, misunderstanding, or even perception and hence, is open to skepticism. Visual illusions, for instance “The Dress” viral image from 2015, can appear to be different to different people.

The human brain is the most complex organ in the known universe.

All human experiences and sensations originate from the brain. While traditional language and culture attribute emotion to the heart, we now know that the brain is the source of all conscious human experience, including emotion.
There are over 86 billion neurons in the human brain. Each neuron is connected to 10 thousand other neurons, resulting in trillions of connections.
A part of the brain that is of major interest is the cerebral cortex, a thin sheet of neurons that composes the highly folded outermost layer of the brain. The cerebral cortex is a very promising candidate for the physical source of consciousness.
The challenge is to relate the subjective first-person account of conscious experience to the observable third-person properties of this incredibly complex organ.

There is a distinction between content of consciousness and states of consciousness.

Content of consciousness refers to specific conscious percepts or memories that are part of the experience of being self-aware. Examples of this include “seeing a red apple,” “having a headache,” or “feeling sad.”
States of consciousness are the different levels of conscious awareness and experience that we all have and that are associated with different patterns of activity. These include wakefulness, REM sleep, and deep sleep. Other less common conscious states include anesthesia, coma, vegetative state, and unresponsive wakefulness.
In order for the cerebral cortex to generate consciousness it has to be aroused (though this is not the only requirement for consciousness). Arousal is a state of neurological activity that requires blood flow, oxygenation, and the presence of crucial neurotransmitters like noradrenaline and serotonin.
Terri Schiavo was a patient in a persistent vegetative state that came to significant media attention due to the legal battle over her continued life support. Patients in persistent vegetative states have sleep-wake cycles and show some motor activity but have no consciousness; they are partially awake and neurologically aroused, but not aware.
Persistent vegetative states and other consciousness disorders allow us to study the basic neurological functions that need to be active for one to experience consciousness at all.