Kinesthetic, Tactile, and Haptic Realms: When you squeeze your phone between shoulder and cheek, you anticipate its texture and weight, adjust your grip so that it won’t slip, and expect those pressures to disappear as soon as you release it. You already know that this object will fall if released from your grasp, or will break when subjected to too large a stress. An immense amount of such knowledge is stored in your spinal cord, cerebellum, and brain—but those systems are so inaccessible that we can scarcely begin to think about them.
Cognitive Realms: We are almost equally inept at describing the systems we use when we think. For example, we are almost completely unaware of how we retrieve and combine the various fragments of knowledge we need—or of how we deal with the risks of being wrong when these involve uncertainties.
The Self-Knowledge Realm: Whatever you may be trying to do, you’ll need models of your own abilities. Otherwise, you’ll set goals that you’ll never achieve, make elaborate plans that you won’t carry out, or too frequently switch between interests—because, as we’ll see in §9 Self, it is hard to achieve any difficult goals unless one can make oneself persist at them.
It would be easy to add to this list of realms, but hard to construct clear distinctions between them.
§6-2. Commonsense Knowledge and Reasoning
Robertson Davies: You like the mind to be a neat machine equipped to work efficiently, if narrowly, and with no extra bits or useless parts. I like the mind to be a dustbin of scraps of brilliant fabric, odd gems, worthless but fascinating curiosities, tinsel, quaint bits of carving, and a reasonable amount of healthy dirt. Shake the machine and it goes out of order; shake the dustbin and it adjusts itself beautifully to its new position.[95]
Albert Einstein: A little knowledge is a dangerous thing. So is a lot.
I once encountered a fellow professor who was returning from teaching a class, and I asked him how the lecture went. The reply was that it had not gone well because “I couldn’t remember which concepts were hard.” This suggests that, over time, such experts convert some of their high-level skills into lower-level script-like processes that leave so few traces in memory that those expects cannot explain how they actually do those things. This has led many thinkers to classify knowledge into two kinds:
Knowing What. These are the kinds of ‘declarative’ or ‘explicit’ knowledge that we can express in gestures or words.
Knowing How. These are the kinds of ‘procedural’ or ‘tacit’ skills (like walking or imagining) that we find very hard to describe.
However, this popular distinction doesn’t describe the functions of those types of knowledge. Instead, for example, we might classify it in terms of the kinds of thinking that we might apply to it:
Positive Expertise: Knowing the situations in which to apply a particular fragment of knowledge.
Negative Expertise: Knowing which actions not to take, because they might make a situation worse.[96]
Debugging Skills: Knowing other ways to proceed when our usual methods fail.
Adaptive Skills: Knowing how to adapt old knowledge to new situations.
The first large-scale attempt to catalog commonsense knowledge was the “CYC” project of Douglas Lenat, which started in 1984, and is described at www.cyc.com. Many ideas in this section were inspired by the results of that project.
Douglas Lenat: “In modern America, this encompasses recent history and current affairs, everyday physics, ‘household’ chemistry, famous books and movies and songs and ads, famous people, nutrition, addition, weather, etc. … [It also includes] many “rules of thumb” largely derived from shared experiences—such as dating, driving, dining, daydreaming, etc., —and human cognitive economics (misremembering, misunderstanding, etc.,), and shared modes of reasoning both high (induction, intuition, inspiration, incubation) and low (deductive reasoning, dialectic argument, superficial analogy, pigeon-holing, etc.).”
Here Lenat describes some kinds of knowledge that a simple statement like this might engage:[97]
“Fred told the waiter he wanted some chips.”
The word “he” means Fred—and not the waiter. This event took place in a restaurant. Fred was a customer dining there. Fred and the waiter were a few feet apart. The waiter was at work there, waiting on Fred at that time.
Fred wants potato chips, not wood chips—but he does not want some particular set of chips.
Both Fred and the waiter are live human beings. Fred accomplished this by speaking words to the waiter. Both of them speak the same language. Both were old enough to talk, and the waiter was old enough to work.
Fred is hungry. He wants and expects that in a few minutes the waiter will bring him a typical portion—which Fred will start eating soon after he gets them.
We can also assume that Fred assumes that the waiter also assumes all those things.
Here is another example of how much one must know to give meaning to a commonplace statement:
“Joe’s daughter was sick so he called the doctor.”
We can assume that Joe cares about his daughter, is upset because she is sick, and wants her to be healthy. Presumably he believes she is sick because of observing some symptoms.
People have different abilities. Joe himself cannot help his daughter. People ask others for help to do things they can’t do themselves. So Joe called the doctor to help heal his daughter.
Joe’s daughter, in some sense, belongs to Joe. People care more about their own daughters than about other people’s daughters. If so advised, Joe will take the daughter to the doctor. When at the doctor’s, she will still belong to Joe.
Medical services can be expensive, but Joe is likely to forgo other spending to get the doctor to help the daughter.
These are all things that ‘everyone knows’ and uses to understand everyday stories. But along with that widely shared, common knowledge, every person also has personal knowledge; we each know our own private histories, characteristics of our acquaintances, special perceptual and motor skills, and other kinds of expertise.
Still, none of our knowledge would have any use unless we also had effective ways to apply that knowledge to solving problems. This means that we also need large bodies of skills for doing what we call commonsense thinking. We’ll come back to that in chapter §7.
96
As suggested in §3-12 we often learn more from failure than from success—because success means you already possessed that skill, whereas failure instructs us to learn something new.
97
See Douglas Lenat,