The Medieval Mind

 

Two Minds Theory (TMT) talks about two different mental systems that all people have, the Intuitive mind and the Narrative mind. These are based in contemporary understandings of neurobiology that were popularized by psychologist Daniel Kahneman, first in his Nobel prize acceptance speech and later in the book Thinking, Fast and Slow. The Narrative mind is logical, sequential, and language-based; it also has some pretty severe limitations on how fast it can work or how many things it can attend to at once. The Narrative mind is also abstract, cold, and disembodied -- these can be good things in some contexts like a legal proceeding, but many people find them alienating in daily life. The Intuitive mind is fast, great at multitasking, often insightful or creative, and expert at tasks that it has performed many times. On the negative side of the ledger, the Intuitive mind is also prone to biases, stereotypes, and dumb mistakes, and because it exists mostly outside of language it can't explain its thinking even when we are aware of its operations (which often we are not). The Narrative mind is based mainly in the outer cerebral cortex, particularly the prefrontal lobes of the brain; the Intuitive mind emerges from multiple systems low in the brain, including the limbic system (emotions), hippocampus (memory), nucleus accumbens (reward system), striatum (habits), and insular cortex (snap judgments). The interaction between these two systems can explain a great deal of human behavior and contributes to how we make sense of the world. 

If Two Minds Theory is true, then it describes general human experiences based on shared human biology. Our biology hasn't changed too much since the last ice age, so I'm always interested in older models of the mind, to see whether TMT can account for fundamental truths that past experts made sense of in different ways. I have previously noted commonalities between TMT and the models of mind and behavior that were proposed by Freud, Aristotle, or Plato. A particularly long-standing model of mind emerged in the Middle Ages, out of interactions between classical sources, contemporary scientific understandings, and the official theology of the Catholic church. The medieval model of mind has been discarded and largely forgotten today, but it was the accepted truth for educated people over a period of nearly 1,000 years. C.S. Lewis in his book The Discarded Image summarizes the medieval view of mind as having three parts: (a) vegetable soul, (b) sensitive soul, and (c) rational soul. The diagram at the top of the page locates these in different parts of the head -- note that the rational soul is at the top of the brain rather than behind the eyes. This may relate to a medieval sense of hierarchy in which everything was joined in a "great chain of being," with the king sitting just under God at the top of the chain. Similarly, medieval scholars expected human reason to be located on top of all our other faculties. But the rational soul matches up fairly well with the Narrative mind in terms of function, even if not location.

Here are the components of the medieval mind according to Lewis, and how they match up with TMT:

Vegetable Soul was the lowest of the three levels, and was shared by humans, animals, and plants. It includes basic bodily functions such as growth, nutrition, elimination, and reproduction. In terms of psychology, the vegetable soul was believed to be governed by a person's individual mix of four physical substances in the body, called the "four humors." The ancient physician Galen identified these substances as: (a) blood, (b) black bile, (c) yellow bile, and (d) phlegm. Having more or less of one of these substances was thought to determine your personality. A "phlegmatic" person, for instance, had an excess of phlegm which made them lazy and slow, but also agreeable. A "choleric" person had too much yellow bile and was angry, excitable, and ambitious. A "melancholic" person had too much black bile ("melancholy" actually means "black bile" in Greek) and was neurotic or depressed. And a "sanguine" person's mix of humors was dominated by blood, which made them active, enthusiastic, and socially useful. The humors were also called "tempers," which is where we get the idea of a "good-tempered" or "bad-tempered" person. Galen's four personality types are not a bad approximation of modern personality theory based on the 5-factor model. The people whom Galen would have considered "sanguine," for example, would probably have been high on extraversion and low on neuroticism, while those with a "melancholic" personality would have had the reverse characteristics. The continuity with modern views is the idea that people's biology affects their behavior; in TMT personality comes in via the Intuitive system based on a person's typical reactions to new situations. Those are based in part on their biology.

Sensitive Soul was the second level in the medieval model, associated with awareness of the world around us ("sensitive" means senses or sensations in this context). Humans and animals had a sensitive soul, but plants didn't. The sensitive soul was connected to the familiar 5 senses that perceive the world around us -- vision, touch, taste, hearing, and smell -- and was also connected to another list of 5 internal senses that perceive states within our own body or mind. The five internal senses were:

• memory - a resource that in our modern understanding is available to both the Narrative and Intuitive minds, but that is more likely to influence Intuitive understandings. I'm not clear on whether medievals would have made distinctions between things like declarative memory and procedural memory. Declarative memories exist in language, which would align them with the the Narrative system in TMT. But I suspect that medieval scholars meant the procedural or Intuitive kind of memory here, because they thought that animals had this capacity even though they can’t speak.
• estimation - having nothing to do with mathematics, this term instead meant something like what we would call "instinct," or a stimulus-response reaction. It fits with modern understandings of behaviorism, or the way in which behavior is shaped by its consequences. TMT suggests that learning and reactions to stimuli happen largely outside of consciousness, as part of the Intuitive mind.
• imagination - to medievals, this word meant thinking rather than creativity, the mental state of "having things in mind." It's interesting that they didn't necessarily believe thinking required language, so “imagination” probably doesn't mean what we would describe as "thought." Instead, it's probably something more like attention -- a semi-Intuitive process, although one that Two Minds Theory actually locates on the border between the Narrative and Intuitive systems. That’s because attention seems to be connected to conscious awareness, and can be directed through deliberate effort, two things that are generally not true of the Intuitive mind.
• phantasy - this was a "higher form" of imagination, and did mean what we would call imagination in modern terms. It involves playing with images, combining and dividing things in the mind. It's interesting that we often connect such things with reason -- indeed, in IQ tests like Raven's progressive matrices we treat them as one of the strongest indicators of rational intelligence! But medievals considered this a capacity that we shared with animals, part of the "sensitive soul." In TMT we would probably consider this a function of the Narrative rather than the Intuitive mind. 
• wit - also called "common sense" (the original meaning of that term), this meant perception, or the experience of pulling together sensory data to make judgments about it. This capability is how we recognize a face that we know rather than a collection of eyes, nose, and mouth -- something that computers have historically had difficulty in learning to do, but that animals can clearly do as well as us (in the case of dogs, probably using smell more than vision). Wit could also be called "apperception" or "recognition" in modern terms.

The capabilities of the vegetable soul were believed to reside in the frontal lobes, as seen in the diagram at the top of this page. But that wasn't based on neuroanatomical evidence from brain-injured patients, as the modern understanding is. Instead it was simple medieval hierarchy at work again, with these "living and animate but not human" characteristics seen as subservient to the higher-order rational soul at the top of the head, and also close to the sensory apparatus of the eyes, nose, and mouth. Again we would disagree about placement -- memory, for instance, depends strongly on the hippocampus which is a deep-brain structure -- but the sensitive soul largely corresponds to the Intuitive mind in TMT.

Rational Soul was the third mental system of the medieval model, and it was the one unique to humans -- the reason that we were considered to be "rational animals." Interestingly, rational soul was a capacity that humans were believed to share with angels, who perhaps did not have the sensitive or vegetable types of mind. Rational soul, then, is what religious people might mean by the word "soul" today, in the sense of personal characteristics and mental states separate from the physical body. But it's worth noting some aspects of mind that are left out of rational soul, such as personality (vegetable soul), memory (sensitive soul), imagination (sensitive soul), and common sense (sensitive soul). Many of these are included in our current sense of self, but might not have been included in the medieval conception. Rational soul could be subdivided into two parts based on the medieval understanding:

• ratio (Latin for "reason") - math and logic, characteristics that TMT clearly links with the Narrative mind. These are abstract and symbolic operations that rely heavily on frontal-lobe processes, and that are expressed using language. They are the verbal, mathematical, and logical puzzle-solving abilities that many intelligence tests measure.
• intellectus (Latin for "intellect") - a capacity different from reason, which provides intuitive understanding. Intellect gives us the "truths which we hold to be self-evident," the first principles or fundamental propositions on which all other structures of logic rest. In the medieval worldview, there were truths that logic alone could never prove, such as the existence of God. These were simply perceived as true. Lewis elsewhere argues that this is true both about mathematics and about morality: "we 'just see' that there is no reason why my neighbor's happiness should be sacrificed to my own, as we 'just see' that things which are equal to the same thing are equal to one another. If we cannot prove either axiom, that is not because they are irrational but because they are self-evident and all proofs depend on them. Their intrinsic reasonableness shines by it own light" (Miracles, 1947, p. 54). 

Perhaps a part of logic is indeed based in perception by the Intuitive mind. But in our modern understanding, much of what the medievals called intellect is often regarded as a form of error, a kind of biased or emotional reasoning that distracts us from truths proved by logic. Once the idea that "X is good for its own sake" was seen as a form of rational thought (intellectus), but now this type of value judgment is understood as an expression of taste, emotion, or culture. When we say that someone is "being unreasonable," we tend to mean that they have faulty logic, or that they are reasoning from bad starting premises. We probably have a different understanding of facts or causal chains than they do. To medieval scholars, it was perfectly acceptable to also use the term "unreasonable" to also describe a person who had the wrong values. We now locate some things in the Intuitive mind that under the medieval model would have been considered also a part of the rational soul or Narrative system.

The medieval model didn't hold all beliefs to standards of evidence or ask people to defend them logically. Steven Pinker argues that this is why modern understandings are better. But it's worth noting that medieval models didn't hold human understanding to be infallible. They also referred to the human capacity for intellect as intelligentia omburata, or "shadowed intelligence." The characteristic of actual intelligentia, or intelligence itself, was thought to be something that only angels possess; our type of intellect was "the shadow of angelic nature in man." In this view, the angelic mind simply perceives all truths self-evidently, without any steps of logical argument. But human perception is cloudy, "seen through a glass darkly," which is why we only get glimpses of truth and must rely on logic and systematic reasoning to fill in the gaps. 

The idea of ratio in the rational soul is clearly in agreement with Two Minds Theory's view of the Narrative mind, but the intellectus or intelligentia dimension of rational soul is generally outside of it. There might be a further opportunity to differentiate the kind of "perception" that exists in the Intuitive mind (e.g., based in the somatosensory cortex) and the kind that is more connected to logical thinking (perhaps located in the frontal cortex instead?). It's definitely false that humans use logic to arrive at every belief, and it's definitely false that all of our non-logical decisions are wrong -- in fact, one insight from Kahneman's description of the Intuitive mind is that our biases and heuristics are correct a surprisingly high percentage of the time. So there's something to be said for an Intuitive-level type of "reasoning" as in the medieval model. 

One massive limitation of the medieval model is that it was used in a time when European civilization was essentially all one culture, dominated by the institution of the Catholic church. A more diverse set of views and experiences tends to challenge the medieval view that truth could be simply "perceived" by the rational soul, because we don't all see things the same way. At the very least, the reality of diversity means that we need to carefully work our way down to just a few generally agreed-upon truths (C.S. Lewis thought that he had found some). Cross-cultural work might help to establish how much of human understanding is in fact innate intelligentia, how much is worked out more methodically using ratio, and how much comes from non-conscious processes like social agreement or "common sense."

The limitations of the medieval model are actually just a few, in comparison to the many areas in which this earlier theory of mind seems to agree with modern neurobiological understandings. And those areas of disagreement present an interesting counterpoint to modern views, perhaps suggesting areas in which it would be beneficial to challenge or perturb our contemporary understanding. Some specific areas for research might be the degree to which perceptions can be expressed in language versus affecting behavior directly outside of language, the extent to which perceptions of truth are shared across cultures, the relative importance of different types of memory in Narrative versus Intuitive thought, and the extent to which non-human animals can figure out spatial-manipulation puzzles that in humans are believed to require use of the Narrative mind. An examination of historical theories of mind can provide us with models that are different enough to suggest novel insights, while also confirming that the fundamental truths of past human experience can still be accounted for by current psychological understandings like Two Minds Theory.