Biology has Darwin’s theory of evolution and physics has the Standard Model but, at present, there is no equivalently unifying theory in the social sciences. This has not been for a want of trying. Psychoanalysis, behaviourism, and evolutionary psychology represent some of the admiral attempts but they have had their critics. The search for a framework bringing together the humanities and also the sciences set the stage for E.O. Wilson’s 1998 book, Consilience: The Unity of Knowledge. Although one of the world’s leading authorities on myrmecology (the study of ants), in his book Wilson discusses possible methods of uniting the sciences and humanities as one.

There are two avenues of thinking that can be taken to unify these subjects, namely, epistemological and ontological unity. Epistemology is the branch of philosophy concerned with the theory of knowledge. For example, a key question in epistemology is “how do we know what we know?”. Ontology is the philosophical study of being, and is centered on problems like “what is a thing?”. However, these abstruse philosophical definitions can be set aside for more distinct real-world examples.

From school through to university, the domain of knowledge is split into different subjects. You learn about glaciers in geography and about WW1 in history. Even though information is siloed into different subjects, the findings from any subject must agree with all others. 2 + 2 = 4 is true in biology, economics, and everything in between. This compartmentalisation of knowledge is a practical measure only, and a forgivable one at that. To master a subject today, it is necessary to become hyper-specialised in one small niche (like myrmecology) because the lines of inquiry now run so deep.

The rise of machine learning is also fueling many instances of crosstalk, by chipping away at the barriers between biology and technology

Now, new fields are starting to pop up in the gaps between the domains. Astrobiology, space law, and evolutionary computing are some examples of this crossover knowledge. The rise of machine learning is also fueling many instances of crosstalk, by chipping away at the barriers between biology and technology. Light is a useful metaphor for here. Before light was understood, colours were thought to be distinct. We now know there are gradations across the spectrum that fill the gaps between them, just like the different disciplines being studied today. While physics and biology might seem like independent avenues of inquiry, there is no bright line between them, and both are seeking the same insights. This is a unity in a horizontal sense, that is, between subjects.

What we’ve described is the epistemological approach to the unity of knowledge, which relies on bridging the gap between different subjects on the basis that they are all tapping into the same underlying truths of the Universe. Ontological unity takes a physical reductionist approach to unifying knowledge, and it is what Wilson argues for in Consilience: The Unity of Knowledge. This has vertical connotations: the subjects are dependent upon one another, with physics at the bottom.

For example, culture emerges from a population, where each person is a biological system. The workings of an individual organism falls under the remit of biochemistry, and ultimately chemistry. At bottom, chemistry is concerned with how atoms and their electrons interact. The study of the fundamental particles that make up atoms is the domain of physics, and this rabbit hole continues on to some form of multidimensional string theory explained by quantum mechanics. This line of reasoning begs the question, can culture be explained by, and hence derived from, physics? If we knew the precise location and momentum of every atom in the Universe, could we calculate every future event?

While interesting, Wilson’s argument that everything can be explained by a minimum common denominator is a hard pill to swallow. Aspects of our society like art and culture, and even consciousness itself, are emergent properties and we cannot learn everything there is to know about them by looking at the atoms of which they consist. For example, artists predominantly paint using colours the human eye can see, rather than in the infrared or ultraviolet portion of the spectrum. That is, there are biological and physical explanations constraining art. However, it would be naive to think this tells us anything useful about the artwork.

Aspects of our society like art and culture, and even consciousness itself, are emergent properties and we cannot learn everything there is to know about them by looking at the atoms of which they consist

A term coined by philosopher Daniel Dennett, a “deepity” is a statement that can be read in two ways: On one reading, it is true but trivial, whereas in another light, it is patently false, albeit more interesting. For example, “age is only a number” is a deepity as this is trivially true: Age is literally just number which increases from birth. However, read another way, it is poking at something more, that is, age is irrelevant. This is patently false. As we get older, we become more mature, our health can deteriorate, and so on. But the phrase “age is only a number” can pose as a profound claim by hiding between these two interpretations. Popular psychology is rife with deepities, and some argue that Wilson’s central thesis is one too. While it is trivially true to say that everything depends on physics (reading #1), to say that from physics we can learn everything there is to know about an emergent property like culture is false albeit interesting (reading #2).

Reducing everything to physics is a neat idea but for now it is just that. Nature cares little for how pretty a theory is and whether the claim is even true is an open question. To try and predict something as complicated as the global banking system on the basis of individual elementary particles is so far beyond our reach, it isn’t a useful lens through which to view the issue. On a practical level, an explanation of a phenomenon should only go one level deeper than the phenomenon itself, so for example the banking system is best understood by examining its constituent parts, namely the banks themselves. It is true that everything in existence is just a manifestation of the energy released in the Big Bang 13 billion years ago but, rest assured, we won’t be deploying the predictive powers of quantum mechanics to solve the housing crisis any time soon.