Can we ever know the truth about reality?
In the fourth century BC, the philosopher Aristotle described nature as having two types of motion: natural motion, which does not require an external force, and violent motion which goes against natural tendencies by requiring an external cause. The natural motion of earth and water is to fall, and air and fire to rise. These were the four terrestrial elements, with a fifth — the aether — in the celestial sphere.
The planets and stars were embedded in concentric spheres that rotated at constant rates. There was no need for gravity, just a tendency for bodies to move along their natural trajectories.
Fast forward to the early modern times of Galileo, then Issac Newton and you’ll find Aristotle’s ideas being dismissed as wrong. After centuries of accepting Aristotelian physics as the truth, it was replaced with completely new laws of motion that described the celestial bodies moving under gravity. The natural motion of planets no longer applied because gravity provided a cause, thus making it violent under Aristotelian physics.
As we approach modern-day, Einstein came onto the scene to completely change and uproot the description of gravity provided by Newton. For one, the idea of an aether — carried across from Aristotle to Newton, albeit in a different form — was scrubbed from textbooks. Space is a vacuum. There are no infinite speeds or instantaneous interactions, and light is as fast as you can travel. There is also no such thing as an absolute reference frame. Even reference frames that disagree on the most fundamental facets of reality, like time and distance, are all accurate measurements of the universe.
Yet, even Einstein’s theory cannot be completely correct.
Throughout history, theories have been found to fall short of describing the truth again and again. These paradigm shifts tell us that even the greatest minds can get things wrong and that we should maintain a healthy scepticism toward anyone who claims to have found the truth, no matter how convincing.
We are no different to the generation of Aristotle, Galileo or Einstein in that we are also living in a paradigm. All our beliefs and thoughts are contorted by the society in which we live, our education and what we accept as already being true. Our future ancestors will look back and think about just how wrong we were, whether that’s in our science, ethics or something we cannot even recognise at present.
For example, perhaps the next paradigm shift will be to rethink the way we treat the billions of animals slaughtered for nothing more than the pleasure of taste every year. Whilst more and more of the population are realising the horror of animal agriculture and distancing themselves from the unnecessary suffering inflicted on these sentient creatures, this is clearly still a major moral blindspot for mankind. With our current regress in the way we treat women and minorities, it can be hard to see change coming soon.
Returning to science, it is worth recognising its humility. It knows that everything, even the most intuitive, prominent theories must stand up to the test of experiment. Even with overwhelming support, it is still never considered true. Only better at making predictions, supporting evidence and explaining features of the universe than the alternatives.
Such an attitude should be adopted with our beliefs. Everything fits into a model that our minds have created. Our model might seem logical and consistent. It might seem to fit the evidence and help us predict the future in a way that nicely explains what we see. Yet we should treat it with scepticism. Changing our minds is our own paradigm shift — the point we overhaul our model, just like Galileo, Newton and Einstein — and start again, rethinking everything.
You can never be right, you can just hope to not be so wrong that your ancestors look back and go what the heck were they thinking?
Or, at least, that is the pessimistic view of things. But could such a viewpoint — one that has been adopted by many minds throughout history — itself be an outdated paradigm?
Hearing Carlo Rovelli speak on this topic last year, he made the case that we shouldn’t think of outdated models as being wrong. If we look at Aristotle, Newton and Einstein, we don’t see different models. We’re simply seeing generalisations of the same principles, with a stronger explanatory and scientific basis.
For example, Aristotle’s notion of natural and violent motion was a case study on Newton’s first law. Something travelling through space would continue to travel until acted upon by another force. That sounds a lot like natural motion, with a force sounding a lot like a cause, which leads to violent motion. This is what Aristotle was describing with the knowledge and experience he had available. Aristotle clearly had a good working model for examples found on Earth and whilst the science was still in need of development, his model was in fact the basis for subsequent theories of motion.
This can be taken further. When Aristotle said an object falling to Earth follows its natural motion, Einstein would say that it is following its geodesic, the fastest path through spacetime. It turns out that the motion of the planets was in fact due to a natural trajectory through curved spacetime all along.
If you take Einstein’s equations and simplify them for most Earthly reference frames, you obtain Newton’s laws. If you simplify Newton’s laws for a person living in the fourth century BC, without access to advanced technology and a vacuum, you obtain predictions made by Aristotle. For example, Aristotle proposed that the velocity of a falling object is related to its weight. Whilst in the general case this is not true — as Galileo showed — it is correct for an object falling through the air on Earth.
When we come up with new ideas, often we’re not starting from scratch at all. Instead, we’re simply building on what came before; realising our model is part of a larger picture. One that includes more parts of the universe, deeper structures or ideas, or perhaps more types of people and animals. Models begin to expire when we realise they fail to consider as much as we once thought they did.
We can never be certain of anything but we can bring ourselves incrementally closer. We do this by continuing to improve, learn and update that model of the world we keep inside our heads. Sometimes this is just about tweaking the parameters, changing a few details, generalising where necessary and optimising for the diverse and complex world we live in.