Philosophers have been puzzling over the 'Brain in a Vat' problem for several decades. The 'problem' comes down to arguments over whether it's possible (or not) to philosophically 'prove' that one (i.e. the observer) is not simply an isolated brain that is, in effect, imagining the entire world around it.

Many treatises have been written about the problem. Some insisting that one could, theoretically, be able to work out if one was simply a brain in a vat - and others which maintain the opposite.

Here are some example papers :

Do You Know That You Are Not a Brain in a Vat? Logos & Episteme, Volume 5, Issue 2, 2014, Pages 161-181

How Both You and the Brain in a Vat Can Know Whether or Not You Are Envatted ^{[ paywalled ]} Aristotelian Society Supplementary, Volume 92, Issue 1, 2018, Pages 151–181

How I Know I’m Not a Brain in a Vat ^{[ paywalled ]} Royal Institute of Philosophy Supplements, Volume 64

Serious theories and skeptical theories: Why you are probably not a brain in a vat ^{[ paywalled ]} Philosophical Studies, volume 173, pages1031–1052(2016)

The prospect of being able to keep an adult human brain fully functioning in isolation is currently extremely remote. On a very small scale however, viable self-configuring collections of human brain cells - grown from stem-cells - are now a lab-based reality.

So-called 'Brain Organoids' have been prepared and sustained under lab conditions by various research groups. Notably, Case Western Reserve University (link) and The University of Cambridge (link).

Production of these 'mini brains' has added urgency to ethical and philosophical considerations of such research.

Note : This article is tagged 'Unfalsifiable' because non-one has yet been able to devise any form of experiment which could either prove or disprove the theory - let alone carry one out.

Also see :Is the Universe a Computer Simulation?plugin-autotooltip__plain plugin-autotooltip_bigIs the Universe a Computer Simulation?

unfalsifiable

The Simulation Hypothesis was first published by Hans Moravec (of the Robotics Institute, Carnegie Mellon University, US) in 1998. See Simulation, Consciousness, Existence

Then, in 2003, Professor Nick Bostrom, Director of the Future of Humanity Institute, Faculty of Philosophy & James Martin 21st Century School, Oxford University, published his paper