An Essay on the Nature of Rationality

By Martin Hunt
Copyright 2000 - all right reserved

A highway with lots of traffic.

How is it possible? Why doesn't it just end up in a horrendous crash?

Because it forms an understandable system. Each participant understands how the other elements behave; the road, their car, the other drivers, etc. If this understanding wasn't possible, then driving in traffic would be impossible.

Mental capacities like understanding are best understood in the context of the evolutionary processes that created them. The simple capacity for understanding is one that we share with all creatures.

The word understanding is ancient - the clear reference to standing under is full of implication. Just what is it that one stands under? Well, you stand under things that you don't think will collapse. The thing stood under, a structure of some sort: say a tree, cave or house, seems trustworthy, and is stood under precisely because it seems trustworthy. So, it seems reasonable to suppose that "to understand" something means to have a mental structure in relation to that something that is reliable enough to trust with your life.

This is what happens on the highway - we form a mental structure of the environment that is equivalent to the environment. We anticipate the results of our actions by visualizing what happens when we manipulate that mental structure and we act according to the outcome of that visualization. On the highway, this whole process is automatic and much of it happens without conscious awareness because the processes of consciousness are too slow to be useful in dangerous situations.

Note that for understanding to occur two things need to be in place; a mind that can understand, and an environment that is consistent with the mental structures that the mind can make. I take it as obvious that the environment pre-dates the mind, and that the structures that the mind can make have grown out of a need to adapt to the environment. It is not a miraculous coincidence that the structures that the mind can make are consistent with the environment - the mind exists only because they are. Creatures that have minds exist only because understanding provides an advantage to the creatures that possess it. That advantage is sufficient to ensure that the present is populated by the progeny of those who were lucky enough possess understanding in the past. The manifest advantage of understanding is enough to allow evolution to create understanding minds in the first place, but also causes the capacities of minds to grow and become more elaborate with the passage of time.

Consider a slug. Not a creature with much mind. But it understands things like "food over there" and "hot underfoot". This very simple level of understanding carries important implications about the nature of the world understood. It implies for instance that "food" is an object with a location that is fairly stable (as far as the slug is concerned). There is no need for the slug to be conscious of the object. All that is required is that the food be detected/approached/consumed. This ability implies that the environment provides things that are detectable, approachable, and consumable, or more broadly, understandable.

The understanding that the slug has presents us with lessons that we cannot ignore. The things that a slug understands are too simple to be wrong. A slug is not, cannot, be mistaken about the existence of food. This is not to say that you can't decieve a slug. A slug may be mistaken about particular instances. But it is not mistaken to understand that "food" is a thing that can be detected/approached/consumed.

What is a thing that understands? A thing that understands is a "mind". A mind is found in most creatures. The mind isn't material - it is not a brain. It is a structure formed by the interaction of a brain, through perception and action, with an environment. Maybe one could say that the mind is a pattern of interaction between a brain and an environment.

Now what happens if we take this mind, this thing that understands, this thing that makes mental structures that are equivalent to an environment, and add to it certain capacities for percieving it's own state? Then, it's own state, the pattern created by the interaction of a brain with an environment becomes a thing that can be understood. We end up with understandings of understandings. On the highway, it's not enough to understand the state of the percievable environment to survive. One has to respond to patterns like: "I'm on the left side of the road; I can't see over this blind knoll" by actions of "move quickly to the right". One has to understand patterns of circumstances, not just circumstances.

We attach the adjectives "rational" or "reasonable" to percieved understandable patterns of circumstances. Humans percieve themselves to be rational because they percieve understandable patterns of behaviour in themselves and others. We say that a behaviour is "rational" when we can place it in an understandable pattern of behaviours. What we call "reality" is rational to the extent that we can detect patterns of circumstances within it.

But recall that "to understand" something means to have a mental structure in relation to that something that is reliable enough to trust with your life. When we are speaking of rationality then, we are talking about the ability to create mental structures, abstract things, perceptions of patterns of circumstances, that are reliable enough to trust with your life.

Recall too that a "mind" is a thing that understands. That is: a mind is a thing that makes mental structures that are reliable enough for a creature to trust it with it's life. So, a "rational mind" is: a thing that makes mental structures of patterns of circumstances that are reliable enough for a creature to trust it with it's life. So far, the only creatures we know that have rational minds are humans.

Rationality/understanding is a function of the way things seem. If we seem to understand something, then it seems to be rational, and we can act according to our understanding. If things do not seem understandable, then they don't seem rational, and we have no clue from how things seem as to how to act. In the world, on a highway for instance, this could be completely terrifying. The capacity to understand, upon which rationality is based, is a capacity constructed by evolution. It's success is depends on a close correspondence between reality and understanding being generated in time for a creature to act.

In non-rational creatures, understanding is directly related to characteristics of the immediate environment. A slug understands that if it responds in a certain way to a certain kind of information that it will eat. It's just percieve and do. But with rational creatures perception has to be interpreted before it is possible to do. The way the environment seems to be is a result of that interpretation.

You're on the highway - in front of you, on either side are people whose stance indicates that they have a rope stretched between them which will snare you. I had this happen to me once as I drove along in a car. If I thought that there was a rope in front of me, then I should try to stop. My understanding lead me to believe that there was no rope present. That's because the pranksters would have been seriously injured if there was really a rope between them and I didn't think they'd do that. If I'd been on a motorcycle, I might have thought differently.

There is no way that direct perception alone will help you in circumstances like this - you need to make a judgement about what this information means before you know what to do. My experience is that one tries to fit the information into a number of different mental structures, until a fit that makes sense (ie is rational) is found. The mental structure with the best fit becomes the the thing understood, or the way things seem to be, and action is taken on the basis of that.

Rationality/understanding is vulnerable to illusion and delusion. The belief in the existence of Santa is reasonable to a three year old because the people depended upon arrange things to make it seem like Santa is really there. There are solemn references from authority figures; there's the evidence of the gifts under the tree and the consumed plate of cookies. Any reasonable person would be taken in by such manipulations, not just kids. Mistaken belief often generates delusion.

Evolution, the process of natural selection, works on populations of related individuals with varying abilities and capacities. The useful ability here may be a handicap there. so we see that the effectiveness of an ability or capacity is contingent upon the circumstances within which it is exercised. The ability to understand rationally depends on an array of more fundamental abilities, such as vision and memory. People possess these abilities and capacities to varying degrees. Therefore people must exhibit varying degrees in their ability to understand rationally. One implication of this is that some people will be much more, or much less able to achieve rational understanding than others. This represents the stupid smart dimension of rationality. Those who are stupid will not be able to understand some things understandable by those who are smart.

But not all variations in rationality can be measured on the scale of effectiveness. Sometimes the perception of pattern A by Bob leads to action just as effective as the action caused by the perception of pattern B by Sue. More often, it is simply difficult to tell which action is more effective. But what seems understandable to Bob, may not be understandable to Sue, and visa versa. Thus, the equally effective actions of one may seem "irrational" to the other.

Rationality/understanding is vulnerable to a narrow perspective. It's possible, by the choice of axioms, to construct structures that are easy to understand, but that have no relation to reality. It's the problem one encounters when trying to investigate reality by manipulating words - it's possible to make grammatically correct sentences that have no connection to what exists.

So, with rationality being vulnerable to all of these sources of error, how can it be trusted? By being thorough about it. One can be rational about rationality. Where the mind that only understands is a structure, a rational mind is a structure of structure of structures. But that whole structure must be something you can understand; something you can bet your life on. A mistaken understanding has consequences that can be detected. A correct understanding has a corresponding set of consequences that can also be detected. The test isn't some abstract idea of right and wrong - creatures with the wrong understanding die, creatures with the correct understanding live and so the future gets filled with creatures whose ancestors had correct understanding.

Function: verb
Etymology: Middle English, from Old English understandan, from under + standan to stand
Date: before 12th century

    transitive senses
  • 1 a : to grasp the meaning of (understand Russian)
    1b : to grasp the reasonableness of (his behavior is hard to understand)
    1c : to have thorough or technical acquaintance with or expertness in the practice of (understand finance)
    1d : to be thoroughly familiar with the character and propensities of {understands children)
  • 2 : to accept as a fact or truth or regard as plausible without utter certainty (we understand that he is returning from abroad)
  • 3 : to interpret in one of a number of possible ways
  • 4 : to supply in thought as though expressed ("to be married" is commonly understood after the word engaged)

    intransitive senses

  • 1 : to have understanding : have the power of comprehension
  • 2 : to achieve a grasp of the nature, significance, or explanation of something
  • 3 : to believe or infer something to be the case
  • 4 : to show a sympathetic or tolerant attitude toward something
Function: adjective
Etymology: Middle English racional, from Latin rationalis, from ration-, ratio
Date: 14th century
  • 1 a : having reason or understanding
    b : relating to, based on, or agreeable to reason
    : REASONABLE "a rational explanation", "rational behavior"
  • 2 : involving only multiplication, division, addition, and subtraction and only a finite number of times
  • 3 : relating to, consisting of, or being one or more rational numbers (a rational root of an equation)
- ra·tio·nal·ly adverb - ra·tio·nal·ness noun
Function: verb
Date: 15th century

    transitive senses
  • 1 archaic : to justify or support with reasons
  • 2 : to persuade or influence by the use of reason
  • 3 : to discover, formulate, or conclude by the use of reason (a carefully reasoned analysis)

    intransitive senses

  • 1a obsolete : to take part in conversation, discussion, or argument
    1b : to talk with another so as to influence his actions or opinions (can't reason with her)
  • 2 : to use the faculty of reason so as to arrive at conclusions


An idea that replicates itself from one mind to the next.


Richard Dawkins says that evolution is "differential survival of replicating entities". So, evolution is a process of selection among variable replicators. Any source of selection, applied to any pool of variable replicators, will create an evolutionary system, with the replicators assuming a closer and closer fit to the characteristics selected for.

I assume that evolution is the process that created the whole of the living world, including humans. Any capacity or ability that creatures have must be considered in the context that creature's evolutionary heritage. One of the implications of this is that any creature now alive, is the descendant of creatures who have been selected (because they survived to have offspring) because they fit better to the requirements of their environment than there less lucky brethren. On an individual level, survival of a creature isn't only a function of it's genetic heritage of course. Luck in the course of life has a great deal to do with individual success. But when populations are considered (pools of replicators), evolution has been demonstrated to be an amazingly powerful fitter of creatures to circumstances.

This has implications for epistimology. It is often claimed that our senses, and mental processes have no necessary connection to reality. This is not so. We have the senses and mental processes that we have precisely because they enable creatures to interact successfully with their environment. The key here is the necessity of successful interaction. Not only must a creature respond correctly or die, it must respond in time. The mosquito that percieves my swatting hand in time to escape will replicate. That's why mosquitos are so darned quick. Often, discussions of assume that knowledge must be perfect to be useful. This isn't so. A quick estimation of the meaning of the relevant circumstances is often much more useful (because it allows response in time) than an exhaustive analysis.

In simple creatures, like say a slug, it's easy to imagine that mental capability is as much specified by evolution as physical features, such as it's size and colour. It responds to touch, and light, and chemicals, but isn't so concerned about gravity. The idea of evolution is often presented as "survival of the fittest" which links nicely to the idea of "Nature - red in tooth and claw". Fitness is then seen as the biggest muscles or the sharpest teeth. This is all a bit ludicrous when applied to slugs. An improved ability to detect food at a distance, would be much more useful to slugs than sharper teeth, and the ability to detect food at a distance is an amazingly subtle ability that opens the door to still more amazing abilities that can build upon it.

If we consider the cat, we consider a creature that seems to fit the "red in tooth" image. Yet even in a cat, mental capacities like sharp hearing, acute vision, and stealthy tread are at least as important as sharp teeth, and are as much a product of evolution.

The point that Dawkins makes about evolution is that the replicating entity is neither the cat nor the slug. Genes are what replicate. Creatures live and die. Genes replicate by creating creatures that succeed in having offspring. Now this may seem pretty complicated - why not just replicate without all the trouble of making the creature? But complication isn't an issue to either the gene or to evolution. If the complicated structure works better than the simple one, then that's the one that goes on into the future.

Dawkins makes the stunning suggestion that genes are not the only replicator on the Earth. He says,
"I think that a new kind of replicator has recently emerged on this very planet. It is staring us in the face. It is still in it's infancy, still drifting clumsily about in it's primeval soup, but alread it is achieving evolutionary change a t a rate which leaves the old gene panting far behind.

The new soup is the soup of human culture."

Dawkins calls this new replicator a " meme ".