Christof Koch is a German American neuroscientist now in his late 60s, who entered the field of consciousness research as a 28-year-old MIT postdoc in the late 1980s. He has a PhD in computational neuroscience from Germany’s Max Planck Institute for Biological Cybernetics and taught at Caltech. As a postdoc, he worked with Francis Crick, the revered scientist who, with others, discovered the double-helical structure of DNA in the 1950s and received the Nobel Prize in 1962. Together, Koch and Crick revolutionized the still-new science of consciousness, believing that they would eventually find the physical, neurological correlates to consciousness in the brain.

In 1998, Koch made a bet to this effect with David Chalmers, which set the stage for the competing theories of consciousness that Pollan explores throughout the book.

Later in life, Koch participated in a psychedelic experience during an ayahuasca retreat during which he felt he accessed a “universal mind” (218). Afterward, he came to doubt his previous assumptions and now sees “the abject inability of physicalism to explain or even deal with consciousness” (219). He has now shifted his research to the theory of idealism, the concept that “the universe itself is made up of mind” (222) and consciousness is an inherent quality of all matter. His transition demonstrates the theme of the Limits of Western Rationality.

David Chalmers is an Australian-born philosopher who studies consciousness. In 1994, he presented a paper at a consciousness conference in which he described the easy and hard problems of consciousness research, a concept that has impacted every study and theory since. He asks the difficult, possibly unanswerable question of why mental operations such as information processing should be accompanied by “any inner feeling” of any kind. In 1998, he made the bet with Christof Koch that science would not locate the physical origins of consciousness in the brain within the next 25 years. He won this bet in 2023.

Since his 1994 debut, Chalmers has taken on the role of critic and devil’s advocate for any emerging theory of consciousness. Rather than championing any theory, he uses his philosophical and analytical prowess to critique any theory until it hits a dead end or falls apart. He is skeptical of even the most popular major theories, such as integrated information theory and global workspace theory. In Chapter 4, Chalmers concludes that even idealism, which he finds implausible, is no more implausible than any other theory. His deep skepticism highlights the limitations of any Western thought, either scientific or philosophical, to adequately solve the mysteries of consciousness.

Stefano Mancuso is an Italian plant scientist at University of Florence, who is part of the loosely-related group of researchers who call themselves plant neurobiologists. He runs the International Laboratory of Plant Neurobiology, where he studies plant intelligence and consciousness. His research has revealed more than three thousand chemicals that plants use to communicate with each other or interact with their environments.

He has studied the actions of plant roots, their ability to move through mazes, and the evidence that suggests plants can sleep. He argues that plants clearly display basic levels of sentience—an awareness of their environments, preferences about conditions, and an ability to respond to their environments intelligently. His research urges Pollan to reconsider the human and animal-centric views of consciousness, thus contributing to the theme of Sentience as a Challenge to Human Uniqueness.

Michael Levin is a highly respected American developmental biologist who serves as the Vannevar Bush Distinguished Professor in the Biology department at Tufts University where he runs two different research labs. His work has been praised by Mancuso and others, who believe he will receive the Nobel Prize eventually. Levin’s work “poses a stiff challenge to modern science’s fetish for both the neuron and the gene” (34). He believes that neurons are not uniquely required for mental processes and consciousness. He also suggests that DNA is the not most important component of living organisms, but rather argues that bioelectricity, which dies with the cell’s death, is the crucial element for organizing and maintaining cellular cohesion.

Levin has created something called a Xenobot, a collection of skin cells from a tadpole that, when separated from the tadpole’s bioelectric field, clump together to form a new kind of organism with its own bioelectric field. He argues that consciousness begins with homeostasis, a crucial concept that influences most current biological theories of consciousness. Moreover, Levin is a gradualist, someone who does not draw a hard line between living beings and other kinds of systems.

He suggests that any system capable of monitoring and responding to its environment (such as a thermostat) could be considered to have some basic level of sentience. Levin is one of several scientists who therefore blur the lines of who or what counts as sentient/conscious, and thus challenges humans’ status as unique in nature.

Karl Friston is a physicist, neuroscientist, and psychiatrist at University College London, whose theoretical work has been deeply influential to many scientists discussed in A World Appears, including Levin and Damasio. He developed the theoretical and mathematical frameworks used in brain imaging and the Bayesian brain model of perception. Friston’s biggest contribution to consciousness research is his theory of the free-energy principle. His principle, built on the concept of entropy, connects homeostasis (as discussed by Levin) to the drive to resist entropy for survival, which he believes to be the foundation of all consciousness.

Levin, along with his protege Mark Solms, believe that any sufficiently complex self-organizing system can demonstrate some level of awareness, agency, and sentience. They argue that because entropy is an integral concept in physics, that homeostasis and therefore sentience are likewise deeply embedded in physics and information theory. This argument puts them in conflict with Antonio Damasio.

Antonio Damasio is a Portuguese biologist and neuroscientist in his 80s, whose 1994 book Descartes’ Error attempts to bring the importance of feelings back into the field of consciousness research. He posits that Descartes’ famous saying, “I think therefore I am” should more accurately be “I feel, therefore I am” (69). He has published many books on the relationship between thinking, feeling, and consciousness, including: The Feeling of What Happens, Self Comes to Mind, and Feel & Knowing.

While Damasio agrees with Levin and Friston that homeostasis is the foundation of consciousness, he believes it is a purely biological phenomenon that cannot be replicated in nonliving things like computer systems. He argues that feelings evolved as a way for the body to transmit information from internal systems to the brain, which he calls homeostatic feelings. He adds that feelings are generated in the brainstem, suggesting that homeostasis and emotion evolved much earlier than higher levels of consciousnesses such as thought.

Damasio also states that the split between body and mind first suggested by Galileo and Descartes created a bias in Western science that privileges conscious thought over the more bodily-centered realm of feelings, thus leading to bias and error in current science. His argument contributes to the theme of The Impact of Biases on Science.

Russell Hurlburt is an American psychologist at University of Nevada, LAs Vegas, who has been studying thought for 50 years. Hurlburt first became interested in describing and understanding people’s inner experiences while serving with the U.S. Army during the Vietnam War. Later, as a graduate student he devised the Descriptive Experience Sampling research method in alignment with phenomenology’s stance that consciousness must be studied from within.

For this method, he developed a rudimentary beeper that is essentially a timer attached to an earpiece that emits a beep directly into the subject’s ear. When the subject hears the beep, they are required to stop and jot down whatever they were thinking the second before the beep. Hurlburt believes it is possible and necessary to isolate individual thoughts from their context of situation and memory to better understand how thoughts occur in the mind.

Pollan resists this conclusion when he participates in the study, believing that some thoughts arise fully formed and cannot be separate from their contexts. Hurlburt states that people experience thought on a spectrum, from fully formed inner speech to images and sensations, to “a world of pure perception” (148) with little conscious thought at all. His conclusion that Pollan sits on this “empty” (148) end of the spectrum deeply impacts Pollan’s perception of himself.

Kalina Christoff Hadjiilieva is a Bulgarian-born psychologist and jazz pianist who studies unconscious or “spontaneous thought” (151), including mental wandering. In contrast with Hurlburt, she argues that thoughts are inter-related and difficult to isolate from each. She uses phenomenological methods and neuroscientific methods in her research to study where and how thoughts arise in conscious awareness. She concludes that thoughts originate beneath awareness and then rise to the level of consciousness.

Hadjiilieva argues that studies of the unconscious and mental wandering have been largely ignored by the scientific community because of propaganda. Mental wandering is important for developing a “rich sense of identity” (158), but it does not produce the kind of work valued in Western capitalist society. Other scientists have therefore formed biased conclusions that constantly engaged and structured thought is better, because it is more beneficial to the current capitalist system. Her argument is another example of the way biases can impact seemingly impartial science.