‘Brain in a Vat’: A Thought Experiment

By Keith Tidman

Let’s hypothesise that someone’s brain has been removed from the body and immersed in a vat of fluids essential for keeping the brain not only alive and healthy but functioning normally — as if it is still in a human skull sustained by other bodily organs.

A version of this thought experiment was laid out by René Descartes in 1641 in the Meditations on First Philosophy, as part of inquiring whether sensory impressions are delusions. An investigation that ultimately led to his celebrated conclusion, ‘Cogito, ergo sum’ (‘I think, therefore I am’). Fast-forward to American philosopher Gilbert Harman, who modernised the what-if experiment in 1973. Harman’s update included introducing the idea of a vat (in place of the allegorical device of information being fed to someone by an ‘evil demon’, originally conceived by Descartes) in order to acknowledge the contemporary influences of neuroscience in understanding the brain and mind.

In this thought experiment, a brain separated from its body and sustained in a vat of chemicals is assumed to possess consciousness — that is, the neuronal correlates of perception, experience, awareness, wonderment, cognition, abstraction, and higher-order thought — with its nerve endings attached by wires to a quantum computer and a sophisticated program. Scientists feed the disembodied brain with electrical signals, identical to those that people are familiar with receiving during the process of interacting through the senses with a notional external world. Hooked up in this manner, the brain (mind) in the vat therefore does not physically interact with what we otherwise perceive as a material world. Conceptualizations of a physical world — fed to the brain via computer prompts and mimicking such encounters — suffice for the awareness of experience.

The aim of this what-if experiment is to test questions not about science or even ‘Matrix’-like science fiction, but about epistemology — queries such as what do we know, how do we know it, with what certainty do we know it, and why does what we know matter? Specifically, issues to do with scepticism, truth, mind, interpretation, belief, and reality-versus-illusion — influenced by the lack of irrefutable evidence that we are not, in fact, brains in vats. We might regard these notions as solipsistic, where the mind believes nothing (no mental state) exists beyond what it alone experiences and thinks it knows.

In the brain-in-a-vat scenario, the mind cannot differentiate between experiences of things and events in the physical, external world and those virtual experiences electrically prompted by the scientists who programmed the computer. Yet, since the brain is in all ways experiencing a reality, whether or not illusionary, then even in the absence of a body the mind bears the complement of higher-order qualities required to be a person, invested with full-on human-level consciousness. To the brain suspended in a vat and to the brain housed in a skull sitting atop a body, the mental life experienced is presumed to be the same.

But my question, then, is this: Is either reality — that for which the computer provides evidence and that for which external things and events provide evidence — more convincing (more real, that is) than the other? After all, are not both experiences of, say, a blue sky with puffy clouds qualitatively and notionally the same: whereby both realities are the product of impulses, even if the sources and paths of the impulses differ?

If the experiences are qualitatively the same, the philosophical sceptic might maintain that much about the external world that we surmise is true, like the briskness of a winter morning or the aroma of fresh-baked bread, is in fact hard to nail down. The reason being that in the case of a brain in a vat, the evidence of a reality provided by scientists is assumed to resemble that provided by a material external world, yet result in a different interpretation of someone’s experiences. We might wonder how many descriptions there are of how the conceptualized world corresponds to what we ambitiously call ultimate reality.

So, for example, the sceptical hypothesis asserts that if we are unsure about not being a brain in a vat, then we cannot disregard the possibility that all our propositions (alleged knowledge) about the outside physical world would not hold up to scrutiny. This argument can be expressed by the following syllogism:

1. If I know any proposition of external things and events, then I know that I am not a brain in a vat;

2. I do not know that I am not a brain in a vat;

3. Therefore, I do not know any proposition of external things and events about the external world.

Further, given that a brain in a vat and a brain in a skull would receive identical stimuli — and that the latter are the only means either brain is able to relate to its surroundings — then neither brain can determine if it is the one bathed in a vat or the one embodied in a skull. Neither mind can be sure of the soundness of what it thinks it knows, even knowledge of a world of supposed mind-independent things and events. This is the case, even though computer-generated impulses realistically substitute for not directly interacting bodily with a material external world. So, for instance, when a brain in a vat believes that ‘wind is blowing’, there is no wind — no rushing movement of air molecules — but rather the computer-coded, mental simulation of wind. That is, replication of the qualitative state of physical reality.

I would argue that the world experienced by the brain in a vat is not fictitious or unauthentic, but rather is as real to the disembodied brain and mind as the external, physical world is to the embodied brain. Both brains fashion valid representations of truth. I therefore propose that each brain is ‘sufficient’ to qualify as a person: where, notably, the brains’ housing (vat or skull) and signal pathways (digital or sensory) do not matter.

Is Mathematics Invented or Discovered?

Posted by Keith Tidman

I’m a Platonist. Well, at least insofar as how mathematics is presumed ‘discovered’ and, in its being so, serves as the basis of reality. Mathematics, as the mother tongue of the sciences, is about how, on one important epistemological level, humankind seeks to understand the universe. To put this into context, the American physicist Eugene Wigner published a paper in 1960 whose title even referred to the ‘unreasonable effectiveness’ of mathematics, before trying to explain why it might be so. His English contemporary, Paul Dirac, dared to go a step farther, declaring, in a phrase with a theological and celestial ring, that ‘God used beautiful mathematics in creating the world’. All of which leads us to this consequential question: Is mathematics invented or discovered, and does mathematics underpin universal reality?

‘In every department of physical science, there is only so much science … as there is mathematics’ — Immanuel Kant

If mathematics is simply a tool of humanity that happens to align with and helps to describe the natural laws and organisation of the universe, then one might say that mathematics is invented. As such, math is an abstraction that reduces to mental constructs, expressed through globally agreed-upon symbols. In this capacity, these constructs serve — in the complex realm of human cognition and imagination — as a convenient expression of our reasoning and logic, to better grasp the natural world. According to this ‘anti-realist’ school of thought, it is through our probing that we observe the universe and that we then build mathematical formulae in order to describe what we see. Isaac Newton, for example, developed calculus to explain such things as the acceleration of objects and planetary orbits. Mathematicians sometimes refine their formulae later, to increasingly conform to what scientists learn about the universe over time. Another way to put it is that anti-realist theory is saying that without humankind around, mathematics would not exist, either. Yet, the flaw in this paradigm is that it leaves the foundation of reality unstated. It doesn’t meet Galileo’s incisive and ponderable observation that:

‘The book of nature is written in the language of mathematics.’

If, however, mathematics is regarded as the unshakably fundamental basis of the universe — whereby it acts as the native language of everything (embodying universal truths) — then humanity’s role becomes to discover the underlying numbers, equations, and axioms. According to this view, mathematics is intrinsic to nature and provides the building blocks — both proximate and ultimate — of the entire universe. An example consists of that part of the mathematics of Einstein’s theory of general relativity predicting the existence of ‘gravitational waves’; the presence of these waves would not be proven empirically until this century, through advanced technology and techniques. Per this ‘Platonic’ school of thought, the numbers and relationships associated with mathematics would nonetheless still exist, describing phenomena and governing how they interrelate, bringing a semblance of order to the universe — a math-based universe that would exist even absent humankind. After all, this underlying mathematics existed before humans arrived upon the scene — awaiting our discovery — and this mathematics will persist long after us.

If this Platonic theory is the correct way to look at reality, as I believe it is, then it’s worth taking the issue to the next level: the unique role of mathematics in formulating truth and serving as the underlying reality of the universe — both quantitative and qualitative. As Aristotle summed it up, the ‘principles of mathematics are the principles of all things’. Aristotle’s broad stroke foreshadowed the possibility of what millennia later became known in the mathematical and science world as a ‘theory of everything’, unifying all forces, including the still-defiant unification of quantum mechanics and relativity. 

As the Swedish-American cosmologist Max Tegmark provocatively put it, ‘There is only mathematics; that is all that exists’ — an unmistakably monist perspective. He colorfully goes on:

‘We all live in a gigantic mathematical object — one that’s more elaborate than a dodecahedron, and probably also more complex than objects with intimidating names such as Calabi-Yau manifolds, tensor bundles and Hilbert spaces, which appear in today’s most advanced physics theories. Everything in our world is purely mathematical— including you.’

The point is that mathematics doesn’t just provide ‘models’ of physical, qualitative, and relational reality; as Descartes suspected centuries ago, mathematics is reality.

Mathematics thus doesn’t care, if you will, what one might ‘believe’; it dispassionately performs its substratum role, regardless. The more we discover the universe’s mathematical basis, the more we build on an increasingly robust, accurate understanding of universal truths, and get ever nearer to an uncannily precise, clear window onto all reality — foundational to the universe. 

In this role, mathematics has enormous predictive capabilities that pave the way to its inexhaustibly revealing reality. An example is the mathematical hypothesis stating that a particular fundamental particle exists whose field is responsible for the existence of mass. The particle was theoretically predicted, in mathematical form, in the 1960s by British physicist Peter Higgs. Existence of the particle — named the Higgs boson — was confirmed by tests some fifty-plus years later. Likewise, Fermat’s famous last theorem, conjectured in 1637, was not proven mathematically until some 360 years later, in 1994 — yet the ‘truth value’ of the theorem nonetheless existed all along.

Underlying this discussion is the unsurprising observation by the early-20th-century philosopher Edmund Husserl, who noted, in understated fashion, that ‘Experience by itself is not science’ — while elsewhere his referring to ‘the profusion of insights’ that could be obtained from mathematical research. That process is one of discovery. Discovery, that is, of things that are true, even if we had not hitherto known them to be so. The ‘profusion of insights’ obtained in that mathematical manner renders a method that is complete and consistent enough to direct us to a category of understanding whereby all reality is mathematical reality.