What is thinking?

Stop and think about it. How many times a day do you utter some variation of the word think?  For example, “I need to think about it,” or “I’ve thought about it,” or “I’ve been thinking about it.”

Now think about this. What is thought? What are you doing when you say you are thinking? The short answer is this: to think is to link. The long answer makes up the rest of this article.

Thinking occurs in the brain-mind. The brain-mind is often described as the most complex entity known to man. A useful strategy for understanding a complex thing is to describe or analyze it as a hierarchy of levels. Each level is characterized by the entities that reside in it. For example, people interact to form the higher-level thing we call a department and departments interact to form the still-higher-level entity we call a company. Note that the entities that reside at each level can be physical things (people) or abstract things (departments, company). Cognitive science, the interdisciplinary study of the brain-mind, sometimes employs three levels of description to characterize cognition—biological, symbolic, and knowledge.

The entities that reside on the biological level of the brain-mind are neurons, or brain cells. The human brain consists of a network of some 100 billion neurons. Each neuron is linked to as many as 10,000 others. Neurons are either active or inactive. When a neuron becomes active it is said to “fire,” meaning that an electrical impulse travels along the nerve cell. The firing of one or more neurons causes one or more other neurons to fire. At the biological level, to think is to link neural activations.

The entities that reside on the symbolic level of the brain-mind are symbols. Symbols symbolize, which is to say that a symbol is a thing that stands for or represents some other thing. For example, a supermarket barcode pattern is a symbol that stands for a product on the shelf. Symbols exist in the brain as patterns of activated neurons. For instance, one set of activated neurons may symbolize the presence, or later recollection, of ‘smoke’; a different set of activated neurons may stand for the presence or recollection of ‘fire.’ At the symbolic level, to think is to link two or more symbol activations, such as would be the case if the activation of the ‘smoke’ symbol caused the activation of the ‘fire’ symbol. Another example would be for the activation of the four symbols ‘1 + 2 =’ to cause the activation of the symbol ‘3.’

The foregoing paragraph briefly describes the central paradigm of cognitive science, which is variously called the Physical Symbol System Hypothesis or the Computational-Representational Understanding of Mind (CRUM). This paradigm holds that thinking consists of symbols and computational procedures that operate on the symbols. Computation is the transformation of one or more symbols (the input) into one or more other symbols (the output) according to a rule—IF input symbol(s), THEN output symbol(s). For example, your brain-mind implements a computation when it transforms the symbol ‘smoke’ into the symbol ‘fire’ (IF smoke, THEN fire). Similarly, your brain-mind executes a computation when it transforms the symbols ‘1 + 2 =’ into the symbol ‘3’ (IF 1 + 2 =, THEN 3).  A rule is implemented in the brain-mind by the physical links between sets of neurons. Computers and calculators manifest their rules by utilizing physical connections on a silicon chip.

The third level of description is called the knowledge level. The entities that reside in this level are the things we commonly call goals, facts, questions, answers, premises, conclusions, and so forth—all of which can be categorized under the more general concept of a thought or idea. A thought or idea is expressed as a linguistic phrase or sentence or as an image (we’ll ignore images in this article). At the knowledge level, thinking consists of linking one idea with another. For example the idea (premise) ‘There’s smoke billowing up from the other side of that hill’ is linked with the idea (conclusion) ‘There must be a fire on the other side of that hill.’

As we’ll see in a moment, the smoke-fire example lays the groundwork for distinguishing rational thought from other forms of thought. The philosopher John Dewey elaborates on this distinction by first examining the broadest way in which the term ‘thinking’ is used and then progressively restricting the mental activities that properly qualify as ‘thought.’ He explains that at its loosest, thought is taken to mean everything that “goes through our heads”—every sensory experience, fleeting memory, and idle imagining qualifies as a thought. With this definition, thought would include the sort of patternless and directionless thinking that is characteristic of daydreaming. One thought simply sets off another, which sets off another, and so on. There is no particular order to our thoughts, and we do not intend for them to arrive at some specific end.

Dewey’s second, more-restricted definition excludes sensory experience. Percepts may be grist for the mill of thought, but they do not qualify as thought itself. We think, or think of, only the things that we do not directly see, hear, or otherwise perceive. Included among the mental phenomena that remain is “imagining.” Dewey emphasizes the sort of imagining that produces a story. When we imagine in this way, he explains, we are more concerned with invention than with producing a faithful record of observation. Imaginative enterprises are more about constructing an emotionally gratifying story (imagine winning the lottery) and less about arriving at a belief about some fact or truth in the world.

For Dewey, the term thinking is properly restricted to just those thoughts that have beliefs as their end products. As he puts it, “Thinking, for the purposes of this inquiry, is defined . . . as that operation in which present facts suggest other facts (or truths) in such a way as to induce belief in the latter upon the ground or warrant of the former.” Thus, Dewey limits the definition of thinking to inferential (linking) operations that produce a belief about some worldly fact or truth. In other words, to think is to link a present fact to a fact that is absent. Or, to put it another way, to think is to link things experienced or known to things not yet experienced or known. In the case of the smoke-fire example, thinking occurs when you link the known fact ‘There’s smoke billowing up from the other side of that hill’ to the yet-to-be-known fact ‘There’s a fire on the other side of that hill’ (which you’ll know for sure when you climb the hill and observe the fire directly).

In short, at the knowledge level of description, to think is to link a known fact to a yet-to-be-known fact. If all this sounds like the stuffy stuff of logic, it’s not. People link known facts to yet-to-be-known facts all the time. The mother links ‘My baby is crying’ with ‘My baby is hungry.’ The businessperson links ‘The new advertisement runs today’ with ‘Our revenue will increase tomorrow.’ The employee links ‘My boss is smiling’ with ‘My boss is pleased with me.’ Sometime today, you will probably link ‘The light has turned green’ with ‘It’s safe to drive through the intersection.’

Sometimes we link a series of ideas together into a ‘train of thought’ or a ‘chain of reasoning.’  Assume that A, B, and C are ideas. We may chain the ideas together by saying that A causes B causes C. Or, A implies B implies C. Or, A depends on B depends on C. In each case, we link one idea to another to create a chain of thought or reasoning.

So, what is thinking?  Stripped to its essence, the answer is simply this.  To think is to link.