How Philosophers and Neuroscientists Define 'What is Consciousness?'

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What is consciousness? This question has occupied philosophers for millennia and remains a major mystery of science today. Aristotle believed that consciousness exists as a continuum. So plants have a nutritive soul, which controls their growth, nutrition, and reproduction. Animals have such characteristics and a sensitive soul that allows them to perceive things and move and have fears and desires. Finally, human beings have all of these characteristics and a rational soul that allows us to reason and reflect.

In the 17th century, inspired by William Harvey’s demonstration that the heart works as a pump, the philosopher Rene Descartes proposed that the rest of the body could be viewed as acting like a machine. Descartes argued that our ability to view ourselves and the world around us in a rational way proved that consciousness was real – his famous ‘ I think, therefore I am’ — yet the complexity of the ‘soul’ meant that the mechanisms underlying it, unlike those regulating the body, would always remain unknowable to science.

In the 18th century, philosophers became more willing to subject consciousness to scientific inquiry. For instance, John Locke and David Hume argued that the mind could be viewed as a ‘blank slate.’ Each human consciousness represents the accumulation of experiences acquired since birth. This viewpoint did not explain how each mind feels like a unified, individual phenomenon, rather than just a mass of unconnected experiences. And by ignoring the role of species and individual brain structure in the formation of consciousness, Locke and Hume also did not explain why two different people growing up in the same environment can turn out radically different in terms of abilities, personality, and temperament. This viewpoint also failed to explain why human consciousness seems to be so different from that of animals.

Gottfried Wilhelm Leibniz envisaged the mind's inner workings as being something like the different pieces of machinery in a textile mill, an important new phenomenon in the 18th century. Yet, he believed that even if it were possible to explore the insides of a human brain in detail, while this would reveal the different brain components, it would not take us any closer to understanding the human mind because of the deeply subjective nature of the human brain each human consciousness.

Leibniz’s skepticism might have reflected how little was known about the brain in the 18th century. Yet as scientific knowledge about this organ has advanced, it isn’t clear that we are closer to a proper understanding of consciousness. The philosopher David Chalmers has expressed this conundrum by what he calls the ‘hard problem of consciousness.’ Chalmers believes that modern neuroscience might soon allow us to understand how we learn, store memories, perceive things, react in an instant to a painful stimulus, or hear our name spoken across the room at a noisy party. But Chalmers sees these as relatively easy aspects of consciousness to decipher, at least given sufficient research time and money.

In contrast, what Chalmers calls the ‘hard problem’ concerns the difficulty of explaining the deeply subjective feelings we all have as individuals to say, a sunset or a work of art, or the very particular way we felt when we fell in love, had our first child, or whatever, in purely material terms. The difficulty in explaining such subjectivity has led some to view explaining consciousness in such a way as ultimately impossible. But surely, such a viewpoint doesn’t take us much further than we got with Descartes. And indeed, some critics have accused Chalmers and other proponents of the ‘hard problem’ of trying to cling on to the idea of a ‘soul’ that will be forever unknowable to scientific methods, just as Descartes did.

The debate about the material nature of human consciousness isn’t just between philosophers on one side and neuroscientists on the other. Daniel Dennett is a philosopher, but he has also championed a strict materialist view of consciousness. Dennett criticizes theories of human consciousness that ultimately rely on some homunculus, or ‘little man,’ directing things from inside the brain. Instead, Dennett proposes a ‘bottom-up approach, which views the human mind as the product of unconscious, evolved processes that somehow combine to provide an individual ‘I’ appearance.

Dennett has also criticized theories of human consciousness that rely on what he calls ‘skyhooks’ – explanations of complexity that do not build on lower, simpler layers. Yet ironically, in his own view of consciousness, Dennett uses what I would consider a skyhook, namely ‘memes.’ Nowadays, this term usually signifies those images or video clips – often humorous, cringeworthy, or carrying some life message – that spread rapidly on social media. But the term was first introduced in the 1970s by evolutionist Richard Dawkins, who argued that ‘just as genes propagate themselves in the gene pool by leaping from body to body via sperm or eggs, so memes propagate themselves in the meme pool by leaping from brain to brain via a process which, in the broad sense, can be called imitation.’ As a description of how popular images can spread rapidly across the internet, almost like a viral infection, this was a remarkably prophetic and insightful vision.

But using memes to explain how human consciousness works is, I believe, idealist because it sees ideas as independent entities separate from the minds they inhabit when what we really need to do in establishing a true materialist theory of consciousness is to show how ideas originate within the brain. And here, Chalmers’ point about a ‘hard’ problem within consciousness research is relevant. Another criticism that one could make about Dennett is that even if his ‘bottom-up’ approach that sees consciousness as something emerging from a mass of unconscious neural impulses is true, that still leaves explaining the deeply subjective nature of individual human consciousness. This is an issue that I will discuss later in this blog.