The term “metaphysics” owes its origin to one Andronicus of Rhodes who lived at around 100 BCE and was an editor of Aristotle’s corpus. Aristotle had something to say about everything and Andronicus was soon confounded with an editorial problem: how to discern the great philosopher’s early works entitled “Physica” (physics) from the ones following it. Unpretentiously, he used the term “Metaphysica” which simply means “the ones that come after physics”. And thus “metaphysics” was born.
In Physica Aristotle enquired upon the nature of things, for instance why some things fall (e.g. rocks) while others rise (e.g. smoke). In Metaphysica he addressed more general questions like what are the basic elements, he critiqued Democritus’ atomic theory as well as Pythagoras’ core idea that everything is ultimately made of numbers, and he discussed – but mostly rejected – Plato’s views which were in many ways similar to Pythagoras. He also theorized about the nature of causes (causality) and pondered upon ontological semantics – what it means to say that something actually exists. Aristotle considered his entire corpus as a concise study of nature and never differentiated between “specific” and “general” questions. For him nature was a seamless continuum.
Nevertheless, his successors many centuries later made the distinction between “physics” and “metaphysics”, the former being the experimental study of nature while the latter the probing of what was beyond the scope of science. So what is the study of metaphysics now? Its domain shrinking as the various scientific disciplines mature, metaphysics is very much in doubt. Most scientists do not think that there can be something in nature resisting the application of the scientific method. Unexplored areas such as dark matter, string theory, quantum gravity etc., although still beyond experimental scrutiny, are not considered metaphysics; they are falsifiable scientific hypotheses, and as such fall well inside the “Physica” of the 21st century.
Nevertheless, there seems to be one last bastion of metaphysics that still holds: consciousness. The epistemological problem with consciousness is that it cannot be measured objectively. Measuring instruments currently available, such as PET or fMRI scans, can really “see” inside a thinking brain and produce bundles of amazing images. Those images however must be corroborated with what the person in the scanner felt or thought at the time of study. In other words the experimenter needs the subjective report (the person describing their experience) of the experimental object (the brain inside the person) in order to validate her results. There seems to be a disturbing gap between the object (brain – third person reporting) and the person (consciousness – first person reporting), that is apparently unbridgeable.
As a last bastion of metaphysics consciousness is a serious one. Consciousness underpins all measurements and, therefore, all of our science and all of our knowledge. We know what we know because we think that we do. If science proves unable to incorporate consciousness in its corpus then we must remain forever skeptical about the nature of our universe and of ourselves. This amounts to a bomb ticking at the foundations of all natural sciences.
In this light, Artificial Intelligence aiming to reproduce consciousness in a medium other than a biologically evolved brain is a heroic attempt to save science. A thinking robot will not be a simple curiosity but indisputable proof that consciousness belongs to the material world.