Most of us have no doubt that our fellow humans are conscious. We are also pretty sure that many animals have consciousness. Some, like the great ape species, even seem to possess self-consciousness, like us. Others, like dogs and cats and pigs, may lack a sense of self, but they certainly appear to experience inner states of pain and pleasure. About smaller creatures, like mosquitoes, we are not so sure; certainly we have few compunctions about killing them. As for plants, they obviously do not have minds, except in fairy tales. Nor do nonliving things like tables and rocks.

All that is common sense. But common sense has not always proved to be such a good guide in understanding the world. And the part of our world that is most recalcitrant to our understanding at the moment is consciousness itself. How could the electrochemical processes in the lump of gray matter that is our brain give rise to — or, even more mysteriously, be — the dazzling technicolor play of consciousness, with its transports of joy, its stabs of anguish and its stretches of mild contentment alternating with boredom? This has been called “the most important problem in the biological sciences” and even “the last frontier of science.” It engrosses the intellectual energies of a worldwide community of brain scientists, psychologists, philosophers, physicists, computer scientists and even, from time to time, the Dalai Lama.

So vexing has the problem of consciousness proved that some of these thinkers have been driven to a hypothesis that sounds desperate, if not downright crazy. Perhaps, they say, mind is not limited to the brains of some animals. Perhaps it is ubiquitous, present in every bit of matter, all the way up to galaxies, all the way down to electrons and neutrinos, not excluding medium-size things like a glass of water or a potted plant. Moreover, it did not suddenly arise when some physical particles on a certain planet chanced to come into the right configuration; rather, there has been consciousness in the cosmos from the very beginning of time.

Image Credit... Ansel Adams

The doctrine that the stuff of the world is fundamentally mind-stuff goes by the name of panpsychism. A few decades ago, the American philosopher Thomas Nagel showed that it is an inescapable consequence of some quite reasonable premises. First, our brains consist of material particles. Second, these particles, in certain arrangements, produce subjective thoughts and feelings. Third, physical properties alone cannot account for subjectivity. (How could the ineffable experience of tasting a strawberry ever arise from the equations of physics?) Now, Nagel reasoned, the properties of a complex system like the brain don’t just pop into existence from nowhere; they must derive from the properties of that system’s ultimate constituents. Those ultimate constituents must therefore have subjective features themselves — features that, in the right combinations, add up to our inner thoughts and feelings. But the electrons, protons and neutrons making up our brains are no different from those making up the rest of the world. So the entire universe must consist of little bits of consciousness.