Why causality (and free will) are dead
Something caused you to click on this post. Or, at least, it’s likely you can identify a clear, well-defined origin to your current state of reading these words. Perhaps you were compelled from the title. Maybe it appeared in your inbox and you decided to give the first paragraph a go. Failing all of that, perhaps you slipped on a perfectly positioned banana skin, executing a flawless mouse click that only the most comedically-inclined cartoon could contend with.
Whilst equations in physics don’t explicitly reference causality, there’s a good case to be made for some type of causal relationship between events. Einstein’s relativity forces a more nuanced take on this, but there is still a persistent intuition that (speed of light permitting) objects influence each other through cause and effect.
Whilst I think a macroscopic definition of causality is helpful, even necessary, for a lot of uses, the mathematical elephant in the room cannot be so easily dismissed. In addition to the absence of causality, equations also eschew any reference to the arrow of time. The two are, of course, infrangibly linked.
Furthermore, there is a special case of causality resulting from conscious agents, better known as free will. To impose causal realism on our universe, we should either construct a satisfactory mechanism for volitional actions or be forced to dismiss it. Whilst intuitively it is hard to give up the idea of free will, the latter is much more easily unified with our understanding of reality. I accept that, in isolation, removing free will is not a sufficient condition for getting rid of causality, but I do think its uprooting naturally fits into the model of causal scepticism that arises when we reduce the universe down to its essentials.
It’s easy to dislike reductionism for its lack of imagination, and a move towards treating emergent phenomena as entirely distinct is becoming more mainstream. Nevertheless, if reductionism contradicts an emergent property, then we should give it precedence. For example, we can set out how thermodynamics works at a microscopic level and a macroscopic one but claiming pressure is anything but the increased collision of particles with the surface of a container would simply be incorrect.
It is, of course, much easier to describe pressure than it is to describe every individual collision but the perception of pressure will always be won out by the physical reality of particle theory. Pressure may also be difficult to predict from the underlying set of microstates, but if we claim that pressure is an ontological feature of reality, then colliding particles must ipso facto be more real.
Causality, I claim, is at best an emergent feature of nature. Prima facie, it appears also as a real feature. However, unlike thermodynamic pressure, we should expect causality to manifest itself at smaller length scales. This, to some extent, is an assertion based on intuition. However one can also claim the slightly more concrete axiom that causality and the flow of time are fundamentally linked. Where time functions, we should expect causality too. On the other hand, we know that pressure, temperature and volume are linked macroscopically but these are all replaced with a particulate description at smaller scales. Hence we do not require any one of them to maintain their explanatory status at these sizes.
This is where causality encounters a problem. The laws of physics give us the power to predict the future trajectories of particles, in addition to determining their past trajectories. Quantum physics introduces an element of randomness (and produces a further interesting discussion reserved for another post) but nevertheless obeys physical principles that average out to predictable outcomes.
The glue that holds each static frame of existence is not the ‘causer’ and the ‘caused’ but an equation that indicates the next stage in a sequential pattern. The collision of two particles, billiard balls, or planets is merely the predictable next step just as in a sequence like 1,2 and 3.
To claim that the motion of one particle causes the subsequent motion of another is to grant special ontological status to an arbitrary piece of a larger puzzle. At an emergent level, we might start to characterise groups of particles as people, planets and billiard balls. We might claim they are causers but, in reality, the underlying picture is that of a concatenation of infinitesimal frames, ordered by what is physically permissible at the next time interval. These frames form a block universe which is the basis of our reality.
All elements of our reality exist simultaneously. With position and momentum (amongst other things) characterising each element and setting out the rules by which they transform into adjacent elements. The arrow of time is nothing more than our consciousness reading the memories formed by our brain’s computation over a series of these elements, connected by physically permissible transitions.
In man’s largely bygone pantheistic era, attribution of effects to supernatural causes was relatively (if not entirely) commonplace. Crop yield, the weather and good old fashioned luck were not merely a physical process but the whim of a vague yet heavily anthropomorphised god.
Whilst the progression of science — unfortunately, made slower by this deeply ingrained attribution — eliminated the most blatant references to supernaturalism, the sentiment has remained. Everything from miracles, to spirits, witches, good fortune and the miraculous healing of an injury that, whilst frequently involving the slightly more sturdy reliance on western medicine, often gets a sprinkling of divine intervention thrown in for good measure.
Even within our current scientific paradigm, we continue to speculate — either poetically or with a tentative feeling of truth — on the intention of particles, measurement and the direct effect of one process from that of a previous one. Perhaps causality fits in with our innate desire to attribute intention to reality? And perhaps that’s why it is so hard to get rid of it.
In man’s journey to demote the supernatural causation to less and less of the universal pie, we must also relegate ourselves. Our brains are bound by the same physical laws as every other part of the universe. Regardless of its emergent complexity, it’s still just a pink blob of carbon atoms with a small electrical signal and a few connections to external sensors.
We cannot possibly freely cause an action, in just the same way nothing can cause anything. Because everything is set out by physics.
The universe knows the positions and momenta of every particle and computes the seemingly subsequent frame of reality without any intervention from us. As a result, the future and past are already laid out. Our faith that time has a clear direction gives us a convenient but illusory way to view the order of the universe. Causality allows us to see events not as sequential but as reliant.
We are simply actors in a performance, playing out our parts as written by science. And whilst we may be performing for the first time, it has already been written. All we can do is experience the sequence of reality as it plays out, one frame at a time.