The Greek physician Hippocrates, who lived around 400 BCE, was the first to emphasise the importance of the body in generating functions such as memory, thought and reason
Hippocrates proposed a purely materialist account of body and mind in which our health and behaviour are governed by four ‘humours’ – blood, phlegm, bile and black bile. Lower passions such as greed and lust must reside in the liver and guts, reason in the head. These ideas persist – we still speak of making decisions according to our heart or our head.
The philosopher Plato, who lived during the same period, rejected this idea. He believed in the soul. These competing theories prevailed until the 17th century, when French philosopher René Descartes conceived the idea that there is a total split between the conscious mind and the body – the dualist concept. He believed that voluntary thought and movement are the properties of an immortal soul.
The dualist concept has endured for centuries. It has been successful probably because, intuitively, we find it hard to accept the idea that ‘mere’ brain tissue can produce feelings and experiences like love, imagination, dreams and passion.
For ages, scientists were reluctant to tackle the issue of mind and consciousness because it was either too philosophical or just too elusive to study experimentally. What actually is ‘consciousness’? How can you measure it?
What is consciousness?
Philosophers have spent centuries debating the nature of consciousness. It remains a highly controversial topic, with plenty of disagreement.
Consciousness encompasses feelings and experience, many of which are purely subjective (the sensation of taste for example, or ‘the redness of red’). These are known as qualia. A major problem for science is to understand how these experiences can arise from the brain’s raw material – the neurons, other types of cells, and surrounding fluids and intercellular ‘glue’ inside our skulls.
Scientists often talk in terms of an ‘emergent property’ – something that happens collectively that would not have been predicted on the basis of what is known of the individual units.
Some neuroscientists call the subjective element the ‘hard’ problem of consciousness. Because it is ‘private’ to an individual, some argue that it is not something that we will ever be able to explain meaningfully.
More conveniently, consciousness can be likened to awareness – of one’s self and surroundings. It is sometimes divided into phenomenal consciousness (P-consciousness), an awareness of what is going on now, and access consciousness (A-consciousness), reflecting internally, drawing on past experience and memory.Lead image:
Wellcome Library, London CC BY