The universe – and our brains – are complex. Western civilisation has passed through differing phases in its treatment of that complexity, but it seems from all the signs that we are on the verge of a new one. In my view that change is potentially Copernican – a major upheaval in our world-view equivalent to realising that the universe does not revolve around us.

In the medieval era, complexity was ignored because of the over-simplifications of the ‘enchanted world’ and its unresolved archetypes. We mistook projections of our psychological functions for ‘real’ supernatural beings. A supernatural world provided a causal explanation for the world around us that prevented us from needing to engage with its complexity. The medieval era was gradually succeeded by the era of mechanistic science, in which linear causal mechanisms took the place of supernatural ones. Although we began to get to grips with the processes in ourselves and the universe, this was at the price of over-estimating our understanding of them, because we were using a naturalistic framework according to which, in principle, all events could be fully explained.

We are now gradually moving beyond this into a third phase of intellectual development. In this third phase, we not only develop models to represent the universe, but we also recognise and adapt to the limitations of these models. We take into account not only what we know, but what we don’t know. The signs of this third phase have been appearing in many different areas of intellectual endeavour.

• In mathematics and allied areas of science, there has been complexity theory and systems theory, which try to take into account the complexity of systems and the unpredictable ways in which complex systems operate, whether those systems involve the human brain, society, or global climate.
• In psychology, cognitive bias theory has increasingly mapped the kinds of errors that lead us to think we know things that we do not. We now recognise increasingly why we are so inclined to over-estimate our own knowledge.
• In cognitive science, linguistics and philosophy, embodied mind theory has revealed how much meaning, the building blocks of belief, is formed not by representations of the world, but by a bodily process that prevents us assembling direct representations of the universe.
• Nassim Nicholas Taleb has charted how much our estimates of ‘probability’ simply do not take into account the limitations of the experience on which these estimates are based, so that we remain unprepared for ‘black swans’.
• Iain McGilchrist, drawing again on the cognitive science of the brain, has charted the extent to which the representations of the left hemisphere of the brain can be built up in isolation from the right, giving us a deluded sense of having the whole picture.

These different types of recent work converge in telling us that we need to recognise the complexity and unpredictability of the complex systems we depend on – whether these are physical, chemical, biological, psychological, or social. Once we recognise how little we can actually predict the world, we have a reason to curb the arrogance of scientific naturalism and see it as an over-interpretation of the changing and fallible information we can gain by applying scientific method. The third phase of intellectual development is one that, at last, takes seriously the scepticism offered by Greek Pyrrhonians and Buddhists thousands of years ago. It does not abandon scientific theory or underrate its value, but offers more precise insights into its limitations.

The third phase has a dialectical relationship with the previous two. The thesis (the supernatural) conflicts with the antithesis (the natural). It is only by recognising the ways in which both of these address conditions that the other does not address that we can develop the synthesis, the Middle Way. The Middle Way, like the supernatural, recognises the limitations of our representations of the world, but like the natural, it also recognises the value of theory supported by experience in positively supporting those theories.

I think another aspect of the third phase must also engage with ethics in a way that none of the sources mentioned above do as yet. The first (supernatural) phase subordinated facts to values, so that we lived in a wholly moral world, whilst the second (natural) phase subordinated values to facts, so that ethics became relativised. The third phase needs to involve a recognition that facts and values are in practice interdependent, and that our ignorance of values is no worse than our ignorance of facts.

I do not want to try to predict the future. This nascent development of the third phase could still fizzle out and come to nothing. But the indications do offer some grounds for confidence that a third way of thinking is taking root. There will always be those who seem incapable of thinking beyond the terms of the first and second phases, or try to appropriate the third phase into one of the earlier ones. But their arguments may become increasingly irrelevant when the advantages of the third phase become better known and articulated.

The judgements we make under the influence of third phase thinking are different from those of the second phase because they can start to avoid the same arrogant disregard of uncertainty. They may at least help us cease making the same mistakes about the environment, about social intervention, about economic conditions or about our personal happiness. Fundamentally judgement in the third phase becomes a matter of balancing belief against ignorance, rather than merely an application of what is supposedly known.  No doubt the third phase may in turn be superseded, but it will nevertheless be an advance on what went before.