What does it mean to say one understands something?
The dictionary lists three main meanings for ‘understanding’:
- the perception and comprehension of the ideas expressed by others
- the power of forming sound judgment about a course of action
- something mutually understood or agreed upon.
So understanding requires
- perception of what is and is not in one’s environment,
- a familiarity with the subject under discussion and
- experience of the consequences of actions and events.
With understanding one can think and act flexibly.
Aristotle (384-322BC) discussed ‘What is’ in his book The Categories.
What exists according to Aristotle (simplifying it rather) are entities or things. For example: a rock, a house, an animal, a person. Entities persist over a period of time and can change their properties and react to events.
Entities have properties such as colour, weight, intelligence etc. Properties can be said to ‘exist’ but they cannot exist without the entity. There is no such thing as the colour ‘red’ without some entity which we describe as red.
This was a big departure from the idea of Aristotle’s teacher, Plato (427-347BC). Plato held that the properties of things were the truest form of existence. Thus all the things we describe as red are pale imitations of the true ‘RED’ which exists in the real ‘World of Forms’. The world in which we live is a mere shadow of the ‘World of Forms’.
The ‘World of Forms’ may seem strange and counter-intuitive. But modern science and philosophy holds to the idea of ‘Natural Law’. This idea comes from the laws discovered in the realm of physics.
Physical laws are not universal generalisations about particular things (cats, desks, planets). They are rather statements about universal properties (eg mass, charge, momentum). ‘Red’ isn’t a universal property but energy is.
Even so, physicists tend to think of objects like photons and electrons as carriers of energy etc.
Plato’s legacy is that some people hold that the world we apparently live in is not the real world.
Those objects in the real world that ‘carry’ understandings are human beings. How they actually do this is the subject of much philosophical debate.
One popular idea is that ‘all thought is computation’. This is known as ‘strong artificial intelligence’ or ‘computationalism’. So understanding is some kind of computation. Computation can be defined in mechanical terms. On this view some configuration of levers and cogwheels can understand something. A thermostat, for example, can understand temperature.
In the 19th century Charles Babbage (1791-1871) published designs for a computer which consisted of cogwheels, cams and so on. It is difficult to believe that such a computer would actually understand anything.
Modern computers do not change this conclusion. They score over Babbage’s computer only in miniaturisation, scale (number of ‘cogwheels’) and speed.
There is a subjective ‘feel’ to understanding something. There is an even more pronounced ‘feel’ to not understanding something (doh!). If humans are mechanical computers of some kind there seems to be no reason why we feel anything. For example, why do we feel pain?
The mathematician Roger Penrose admits he doesn’t really know what ‘understand’ means. He thinks this is because he is a mathematician. Mathematicians do not need precise definitions of things they are talking about. They only need to say something about the connections between them. [Penrose 1993]
Penrose thinks computationalism must be wrong: some mathematical things are not computational. For instance, there is a conjecture due to Goldbach (1690-1764) that every even number can be expressed as the sum of two primes (eg 40 = 17 + 23, 198=97+101). There is no computer program that can verify or refute this conjecture. Trials show that it is true up to about 10^18.
Penrose holds that a specific set of rules do not make up ‘understanding’.
Another idea is that the mind consists of ‘units of cultural transmission’ called ‘memes’. The biologist Richard Dawkins coined this term by analogy with ‘gene’. Various principles, catch-phrases, fashions, ways of making pots, even tunes are ‘memes’.
“Memes propagate themselves in the meme pool by leaping from brain to brain via a process which in the broad sense can be called imitation.” [Dawkins 1976]
Philosopher Daniel Dennett takes this up:
“A human mind is itself an artefact created when memes restructure a human brain in order to make it a better habitat for memes” [Dennett 1995.1]
Dennett expands this idea: “A scholar is just a library’s way of making another library” [Dennett 1995.2 ]
Dennett provides no commentary on how memes replicate. Do they blend like cake ingredients or do they have dominant/recessive characteristics like genes? [Orr 1996]
So ‘understanding’ on this view is having the appropriate meme in operation at the appropriate time. Do you have a library?
There are some people who think that the only understanding there is is scientific understanding. For instance, the neuroscientist Sam Harris claims that
“questions of right and wrong, good and evil are questions about human and animal well-being. The moment we admit this we see that science can, in principle, answer such questions – because the experience of conscious creatures depends on the way the universe is.”
‘Well-being’, according to Harris, includes not only happiness, but also “truth, justice, fairness, intellectual pleasure, courage, creativity and having a clear conscience.” This approach to morality “will completely dislodge religion from the firmament of our concerns. The world religions will land somewhere near astrology, witchcraft and Greek mythology on the scrapheap. In their place we will have a thoroughgoing understanding of human flourishing.” [Gefter 2010]
This view is an example of ‘scientism’ . This is the belief that the methods of the physical and natural sciences are appropriate (or even essential) to all other disciplines. Including philosophy, the humanities and the social sciences. [Burkeman 2013]
So what are the methods of the natural sciences? Some eminent scientists such as Sir Percy Medawar (1915-1987) contend that there is no such method. Consider a ‘scientist’ who set out to find a cure for (say) rheumatoid arthritis. He would fail only because he did not know the ‘scientific method’ or he was too lazy to apply it. In either case he should be fired. [Medawar 1984]
Perhaps the best exemplars of our understanding are the sciences. But this does not mean that the only understanding there is is through science. People understood a lot about a lot of things long before science was formulated as a discipline (if it ever was).
Philosophers Bennett and Hacker contend: “it is absurd to suppose that science … is the primary measure of what does and does not exist. One needs no science to discover…that there is a tree in the garden or that there are no trees in one’s room.” [Bennett & Hacker 2003]
But we can say what scientific theories and discoveries have done for us. They explain phenomena. They enable us to predict new phenomena. They enable us to some degree to control the area under study.
Generally understanding proceeds from explanation through prediction to control, but not always. Steam power was controllable before there was any proper explanatory theory.
From this we can define ‘understanding’ in operational terms:
‘Understanding’ is the appreciation of the properties and behaviour of things in the real world to the point where we can
- explain phenomena and events,
- predict new ones and – ultimately
- control them.
It is not necessary to be able to do all three perfectly: there are degrees of understanding.
A thermostat fails the test.
The ‘ability of humans to perceive, understand, imagine, communicate and act’ is the fundamental starting point for any theory of the mind.
You will find this discussed in the first chapter of my book ‘Rethinking the Mind’.
[Aristotle c330BC] The Categories (transl WD Ross) available at
[Bennett & Hacker 2003] Bennett MR & Hacker PMS The Philosophical Foundations of Neuroscience Blackwell Publishing p374
[Burkeman 2013] Burkeman O “‘Scientism’ wars: there’s an elephant in the room, and its name is Sam Harris” The Guardian 2017/8/27 available at https://www.theguardian.com/news/oliver-burkeman-s-blog/2013/aug/27/scientism-wars-sam-harris-elephant
[Dawkins 1976] Dawkins R (1976,1989) The Selfish Gene Oxford University Press p192
[Dennett 1995.1] Dennett D Darwin’s Dangerous Idea Penguin p365
[Dennett 1995.2 ] Dennett D Darwin’s Dangerous Idea Penguin p346
[Gefter 2010] Gefter A “Crusader for Science (interview with Sam Harris)” New Scientist vol 208 (2782) p46-47
[Medawar 1984] Medawar P The Limits of Science Oxford University Press p51
[Orr 1996] Orr H A “Boston Review: Dennett’s Strange Idea” available at
[Penrose 1993] Penrose R Shadows of the Mind Vintage p68