Experimental metaphysics has become viable, and almost nobody is aware of that. But first, what is metaphysics? The first publisher of Aristotle’s writings (the philosopher Andronicus of Rhodes – 1st century BC) literally named the books that followed the books on physics: ‘ta meta ta physics’, meaning ‘ that which comes after the physics books’. Aristotle did not use the term metaphysics himself, but spoke merely of ‘the first philosophy’.
Wikipedia: Metaphysics is the branch of philosophy that examines the fundamental basic structure of reality. Do not confuse this with the examination of the aspects of reality that are open to our sensory or instrumental observation, that’s what physics does.
In other words, Metaphysics is the branch of philosophy that deals with the deep foundations of the world: the nature of space, time, causation and existence, the foundations of reality itself.
Metaphysics is therefore not about sensory experience, which is ultimately the way every aspect of reality enters our consciousness, but about the basis of reality. Not how it works but what it IS. It should be the mother of all philosophy, but from the 19th century on it became a branch of philosophy that was no longer considered really that important since the hugely successful department of physics was considered the branch of science that would from then on deliver all answers about how the world works and why. Which is something that is still is professed and believed by many. Metaphysics is often relegated to the same dubious department as the occult as can be inferred from the following statement from Nobel laureate for Medical Physiology Charles Richet (1850-1935) where he also points to the hopefull possibility of experimental metaphysics:
Metaphysics is not yet officially recognized as science. But that will change... In Edinburgh I was able to confirm to a hundred physiologists that our five senses are not the only way through which knowledge can be acquired and that part of reality is sometimes in other ways reaches consciousness... Just because a fact is rare doesn't mean it doesn't exist. If something is difficult to investigate, is that a reason not to want to understand it?... The people who have taunted metaphysics as occult science, will be just as ashamed as those who protested vehemently against chemistry because seeking the philosopher's stone would be an illusion... As a principle of investigation, only the starting point of Lavoisier, Claude Bernard and Pasteur should apply: to work experimentally always and everywhere. Let us therefore welcome the new science, which will change the direction of human thinking.
One reason that, despite Richet’s emphatic plea, experimental metaphysics didn’t really take off at the time is that the assumptions about the ground of reality were considered untestable. Physics would not have the necessary resources to do metaphysical tests. At about the time of the turn of the 20th century, however, it was gradually becoming clear that metaphysics was indeed beginning to play the role Richet hoped for. We became able to put our metaphysical assumptions to the test.
Bell experiments and spacetime ideas – experimental metaphysics for a Nobel Prize
The Bell experiments that were carried out at the second half of the past century and into this century, and for which in 2022 a Nobel Prize has been awarded, are in their deepest nature metaphysical experiments. The experiments performed with gravitational waves predicted by Einstein’s theory of gravity are also ultimately metaphysical experiments. Measuring and demonstrating gravity waves means that the spacetime fabric – what is it? – is elastic and can carry waves. What is measured there is the effect of these waves on material objects, not the waves themselves, nor the spacetime fabric. If the theory of relativity is correct, and all experiments have confirmed it so far, then causality, that’s cause and effect and its order, is no longer an objective fundamental reality but a consequence of the observer’s individual perspective. The same is true for space and time, they are not as fundamental as we supposed. So, these theories and objective experiments have already clearly a metaphysical tenor. With the Bell experiments quantum physics also starts to offer the opportunity for in-depth metaphysical experiments. That’s the topic I want to discuss here.
The Bell experiments answer a deep question about the nature of reality. The question is whether that reality matches our intuitions. Those intuitions put to the test in these experiments are, to be exact, our inherent assumptions about locality (the assumption that things separated in space cannot influence each other instantaneously) and about realism (that things exist without having to be measured. The Bell experiments have shown already that at least one of those two assumptions is not true. That such an experiment made many physicists uncomfortable is evident from the fact that when John Clauser conceived the idea to setup a Bell experiment, and consulted John Bell about it, the latter asked concerned whether Clauser had a tenured post.
In the meantime, metaphysical experiments are back on the agenda through these questions and experiments and the first performers of these experiments, Clauser, Aspect and Zeilinger, were awarded a joint Nobel Prize in 2022. That is well considered a Nobel Prize for experimental metaphysics.
Testing alternative realities
Another experiment of this type, published in 2019, has, unfortunately, received little attention. It is a variation on Eugene Wigner’s thought experiment. In that experiment, Wigner’s friend conducts a quantum experiment in which the observation of that friend causes a quantum collapse – a positive or negative polarization of a photon, for example. However, outside the laboratory stands Wigner who has not yet observed what happens in the laboratory. The door is not opened yet. For Wigner, who stands outside, his friend and his experiment are quantum entangled and there is therefore no quantum collapse yet. In Wigner’s reality, the quantum collapse on observation only happens when he opens the door of the laboratory. Wigner’s thought experiment is in itself is already a metaphysical thought experiment about how the universe manifests itself with multiple observers.
C: Alternative realities tested with two entangled Wigner’s friend experiments.
But this 2018-19 experiment goes a step further than a single Wigner’s friend experiment and tests whether several observers in two entangled Wigner’s Friend experiments always observe the same result. It is going too far here to describe the experiment in detail, but the results of the experiment answers the metaphysical question whether the next three assumptions about reality also all three are true:
- Locality (no instantenious remote action, mutual effects with maximally the speed of light)
- Freedom of choice for each experimenter
- Absoluteness of observed events (everyone always observes the same outcome)
The result of the experiment – provided that we accept that the detectors used here can be considered as observers – is with a great certainty that at least one of these three metaphysical assumptions is not true. The road to metaphysical experiments without an occult label being immediately affixed to it seems open.
If detectors and other instruments can be considered as observers in quantumphysics is a topic for a next blog, but consider this. All our senses can be considered as instruments feeding experience in our consciousness. Instruments are just extensions to our physical senses and their purpose is the same, evoking ultimately the experience of observation in our consciousness. So, every observation has to end in consciousness and is only experienced there. So, it’s not really about what observers are, it’s about experiencing in the end. We always observe the universe through physical instruments, be it your eyes, ears, fingertips or a proton accelerator. Consciousness is required for experience which is always the product of observation.
For those who want to know the ins and outs of experimental metaphysics, I refer them to the Quanta Magazine article ‘Metaphysical Experiments’ Probe Our Hidden Assumptions About Reality’ or watch the Essentia Foundation YouTube movie ‘Experimental metaphysics with first-person perspectives, by Dr. Eric Cavalcanti’.
Or read further on this website:
Paul J. van Leeuwen graduated in applied physics in Delft TU in 1974. There was little attention to the significance of quantum physics for the view on reality at that time. However, much later in his life he discovered that there is an important and clear connection between quantum physics and consciousness.