Some mental states are selected for (by Darwinian natural or sexual selection) because they cause specific kinds of behavior. I think an emotion is such a mental state combined with a perception on the part of the agent that they are in that state.

The perception aspect of it is essential, I think. We may talk in shorthand of “angry wasps”, but wasps only behave as if they’re angry, unlike dogs, say. To genuinely have an emotion of anger, agents must perceive themselves as being in that state, so that they have a distinctive experience of it, and can reflect on it a bit, maybe even giving some thought to “giving it free rein” or “reining it in”.

To perceive our own mental states, we need to recognize them for what they are. This involves identifying them as belonging to this or that category. How do we learn to do this? First, we learn to recognize the mental state in question by the distinctive behavior it causes in others. Then we learn to “spot the signs” or inner feelings in ourselves — urges, if you like — that accompany our own propensity to behave in similar distinct ways.

So how “private” are emotions? Natural selection creates and shapes emotions for the behavior they cause: in other words they have a public purpose. And furthermore, we initially identify and categorize emotions with reference to public criteria. This makes emotions a much more public matter than has traditionally been supposed. Like the identification and categorization of private experiences of color, the identification, categorization, and therefore understanding of emotions depends on shared activities. Yes, with effort we can sometimes keep an emotion under wraps, but this is the exception rather than the rule. And we usually only try to do so when we think it’s to our social advantage to do so, social advantage being another thing we learn to recognize through swimming in a social sea.

Obviously, emotions have both public and private aspects, and because it can be advantageous to have a particular emotion or to seem to others to have it, they are liable to be faked. (Keeping emotions under wraps as mentioned above is one sort of fakery.) In other words, in some respects they work like signals. Rather as butterfly wings can exhibit fake eyes, some expressions of emotion aren’t quite what they seem. There can be social advantages in faking contrition, for example, or in faking emotional attachment.

Here things get a bit murky, so what I say here is tentative. In general, the possibility of fakery can result in a sort of arms race in which potential dupes get better and better at spotting fakery, while fakers get better and better at producing it. Usually, “costs” increase — ideally to the point where fakers are no longer prepared to pay. But close to that threshhold, both fakers and non-fakers pay a lot. Furthermore, there is a blurred line between fake and genuine emotions, because emotions are not literally true or false. Both fake and genuine expressions of emotion — and thus emotions themselves — can become a more or less deliberate “extravagance”. One might declare his love by threatening to play piano in public ad infinitum, another might proclaim their grief by self-harming. Are genuine or faked emotions behind such activities? It seems to me the question should be how appropriate such emotions and expressions of emotion are in the circumstances. The appropriateness in question is not moral so much as “theatrical”. Is this agent “playing to the gallery” or “laying it on with a trowel”? James Joyce expressed this idea brilliantly when he characterized sentimentality as “unearned emotion”.

The word ‘qualia’ seems to be entering everyday usage. (It’s a plural — the singular is ‘quale’.) A quale is a distinctive sort of conscious experience, such as the subjective experience of blue (i.e. what we consciously experience when we are actually looking at a clear cloudless sky, or dreaming about swimming in the Aegean, etc.). How might qualia be explained from the perspective of evolutionary theory?

The really mysterious thing about qualia is this. The nerve endings send “signals” to the brain via the sensory neurons, like messages along telephone wires, and the brain reacts appropriately by sending “signals” back along the motor neurons to the muscles. Although there is an obvious need for the nerves to work like telephone wires, there doesn’t seem to be any obvious need for conscious experience to enter the picture at all. And yet, the life of a conscious creature is a riot of subjective experiences — distinctive colors, various subjective feelings such as hunger and pain, and so on. Why?

Here’s a very quick answer:

All living creatures are programmed to seek goals such as food, reproduction, safety, etc. Having an internal “map” of the outside world helps animals to achieve these goals. This internal map is a belief system. It works like the onboard computer map in a cruise missile, which looks at the terrain below and guides it towards its target. Of course, a cruise missile has just one goal and a very limited sort of map, but the basic idea is the same.

Programming a cruise missile is no doubt complicated, but maintaining a belief system is even more complicated: it calls for a lot of self-regulation. A belief system needs to perceive situations in the outside world, naturally, but it must also make choices, delay the achievment of some goals in favor of others, discard some beliefs when other beliefs are more likely to be true, and so on.

All of that entails having a higher-level “map”. This is more than just a “map” of the outside world like a cruise missile — it’s a “map” for perceiving one’s own internal states, and one’s overall position in the world. For example, discarding one belief in favor of another belief involves having second-level beliefs about which first-level beliefs are more likely to be true than others.

We are now in a position to ask: what is consciousness? Answer: consciousness is constantly-updated knowledge of our own states — and it mostly consists of higher-level states like the ones just mentioned.

For example, consider reaction to injury. A creature that does not have any such higher-level states (and is therefore not conscious) might have a simple defense mechanism that makes it recoil defensively when injured. But a creature with a higher-level “map” of its own states would be able to make a decision between “carrying on regardless” if the injury is not too serious, or stopping and nursing the wound if the injury is sufficiently serious. The seriousness of the injury depends on the circumstances. If the creature is running away from a predator, it should keep running at all costs. If the creature has to suffer no worse a fate than going without a meal, it should stop and rest. Unless it is in danger of starving to death, in which case it shouldn’t.

The decision-making capacity of these second-level states is a bit like the decision-making capacity of a political assembly. Each of the members wants what’s best for his own constituents, but the decisions of the whole are taken in the interests of the whole. This is achieved when the representations made by each member has its own distinctive character and a degree of insistence.

For example, having a distinctive sort of pain is normally the same thing as having an injury in concert with an internal state that indicates the severity and location of the injury, so that the “assembly” of second-level states (i.e. consciousness) can make an informed decision about whether or not to override it.

As a first pass, above, I said that consciousness is constantly-updated knowledge of our own states. Now I will fine-tune that by saying that consciousness consists of second-level representations of first-level representations of states of the world outside our heads.

For example, suppose I burn my finger. That is a state of the world (my body) outside my head. The injured part of my finger sends a signal to my brain, which then forms a state that normally co-occurs with that sort of injury, and so works as an “indicator” of its presence. This is a first-level representation of such an injury. So far, consciousness has nothing to do with the process. But now my brain has to take account of my overall state, and make decisions based on the various indications that are available to it. Doing that involves perceiving various internal states — such as the first-level representation of the injury to the finger — and weighing them up in terms of their urgency, type, and so on. That involves forming a second-level representation of first-level representations. In a sense, each of the first-level representations has to “make a case” for itself by having distinctive qualities that demand more or less attention, this or that type of attention, and so on.

In order to be represented appropriately at the second level, a first-level representation has to be distinctive. That is why it “feels like something or other”. What these states feel like is a product of how they are physically realized, whether they are welcome or unwelcome, what sorts of decisions have to be made given their occurrence, and so on.

For example, the first-level states that occur with injury are realized in different ways depending on which part of the body is injured. Almost all of them are unpleasant, because almost all injury is unwelcome. Most of them are “insistent” because most of them require some sort of action, taken sooner rather than later.

Or again, consider the first-level states that typically occur with the presence of an (objectively) blue object. Blue objects are unusual in nature, so the second-level states that accompany them are very distinctive, they arouse curiosity, and so on. Mostly these states are pleasant because most blue objects are safe, and some are valuable in some way. The second-level state that accompanies the perception of a blue object (i.e. the “experience of blue”) is not an especially “insistent” sort of state because action is rarely needed in response to the presence of blue objects.

I hope it’s reasonably clear that having “qualia” is a “functional” business that can add significantly to reproductive success.

Some people who are terminally ill or in constant pain kill themselves to end their suffering. I think that’s a perfectly reasonable and decent thing to do.

But most suicides — especially among physically healthy people — are not like that at all. I think they’re motivated instead by the urge to “leave a trail of destruction in one’s wake”. This destruction takes the form of a slow train-wreck of blame and shame on the part of those who are left behind. Suicide prompts inevitable questions and invites a particular sort of interpretation: “What drove him to it?” — “It must have been his ____ [fill in blank here with name of supposed oppressor]. — How horribly they must have treated him! Shame on them!”

Self-harm is usually a passive aggressive activity. It’s manipulative. In a disguised way it’s intended to cause more harm to peripherally “blameworthy” people than to the immediate “victim”.

Suicide is the ultimate in self-harm, and so the ultimate in passive aggression. It exploits our taboos as expressed in phrases like “we mustn’t speak ill of the dead”. Because it is verboten to utter bad thoughts about the dead person, yet something undoubtedly bad has taken place, there is a “finger of blame”, but it cannot be pointed at the “victim”. We are inclined to be inventive, and re-direct our condemnation towards “those who victimised the victim” (who are usually imaginary).

This is the sly thinking of hunger strikers, suicide bombers, and those who exploit children by forcing them to become “suicide bombers by proxy”.

Of course many suicidal people are depressed. And depressed people deserve sympathy rather than condemnation. True. But depressed people are ill, and illness is better treated with honesty than deception. Depressed people are often angry. Angry people are often aggressive, and sometimes do violent things. These things are no less violent for being done by depressed people. We fail to understand suicide if we treat those who kill themselves with unquestioning, saccharine reverence. And quite apart from failing to understand them, we foster an atmosphere in which further potential suicides are more likely, because their intended effect is more clearly guaranteed.

I’ll say that again: if we treat people who kill themselves with too much reverence and respect, we encourage further suicidal behaviour. This probably helps to explain why suicides often break out like “epidemics” in close-knit rural communities.

Instead of wringing our hands, beatifying the dead, and apportioning blame to the living, I suggest that we reserve our sympathies for the living and if necessary adopt a gallows humour or even mockery for the dead. Don’t worry about hurting their feelings, they can’t feel a thing.

Most things of value in life depend on luck. But what is it, exactly, to be lucky?

I think an agent is lucky when he wants something (i.e. he has a goal) and then passes through a sort of “trial” in which getting what he wants is statistically unlikely, or at least not guaranteed. If he passes the trial and gets what he wants, he’s lucky.

For example, suppose six people play a game of pure chance (to keep this example simple). In the long run, over repeated plays, each player will win about one sixth of the time. Assuming a player’s goal is to win, winning is lucky. A single win is lucky, and repeated wins are lucky: in the long run, winning more than one sixth of the time is lucky. Because the relevant sense of probability here is statistical, we have to imagine repeated events of a similar sort, and what proportion of them would achieve the goal.

Three observations can be made here. First, luck depends on having a specific goal and a clear reference class. The reference class consists of repeated events of a similar sort, a relevant proportion of which achieve the goal. It is often implicit — in the present example, it consists of plays of the game. Suppose we keep that reference class, but change the goal. Suppose a player just wants to have fun rather than win. If he has fun in two thirds of the games he plays, he’s more often lucky than unlucky, because a higher proportion of the same class of events count as successful given the agent’s specific goal. Being lucky can become so routine that we’re less inclined to call it good luck, and focus instead on the less usual case of being unlucky. But the basic idea is the same.

Second, an agent can’t be lucky if there is no possibility of his being unlucky. If some members of a class of events are lucky, then some other members must count as “unlucky”, or at least as “less lucky”.

Third, luck applies to events that are more or less beyond our control. Lucky or unlucky events happen to agents, rather than being done by agents.

If we’re lucky, we’ll inherit good genes from long-lived parents. If we’re lucky, we’ll be engaged in projects in life which go well for us, so that we advance towards our goals. If we’re lucky, our lovers will be faithful and honest. These examples of good luck can only happen to genuine agents who have goals — real goals that are the objects of genuine desires. They only count as cases of good luck because things might have been different — there are other cases of the same sorts of events that count as bad luck. And alas, we don’t have much control over them.

For most of the course of a normal life, it would be remarkably bad luck to die while asleep. So we’re not much inclined to call it “good luck” when we simply wake up in the morning as usual. But I think it’s salutary to think that way. In all human life there is an attrition rate. Nowadays, most of us in the West live in unusually safe circumstances (low infant mortality, good health, peace, prosperity) in which we are liable to forget that “in the midst of life we are in death”. An awareness of our own mortality need not be morbid, nor even pessimistic. It can help us get our priorities right. And it serves to remind us that even routine things depend on luck, however secure they may seem.

One sort of event often assumed to be “lucky” is the emergence of my self, starting with conception in the womb. The thought goes something like this: “so many different combinations of sperm and egg might have met at the crucial moment, with different DNA, in which case someone else would exist rather than me — how very lucky I am to exist, when it might so easily have been different!”

But I think that is a mistaken thought. Furthermore, I think it contributes to bigger philosophical problems concerning personal identity, consciousness, and even bad science.

At the moment of conception, the future agent who is being conceived is not yet an agent. Even if we think of the zygote formed at conception as a “potential person”, no merely potential X is a real X, so again no agent actually exists. And where there is no agent, there is no goal of staying alive. Where there is no such goal, there is no proportion of “successful” events in which the goal is achieved. So luck as understood here isn’t involved. There were countless other possible outcomes, but the actual outcome was not “unlikely” in the sense that an amazing coincidence occurred. It’s a bit like being allocated a car registration number — it’s “one in a billion”, but it’s not anything to be surprised about unless you bet beforehand that you would be allocated that very number.

Yet a widespread sense of perplexity persists, and I think it reveals something significant. It shows how much difficulty we have identifying our selves with physical objects (i.e. functioning brains). Despite near-universal agreement that Descartes’ “immaterial substance” is a fantasy, we are fixed in our ways, and we retain a habit of supposing that my self (i.e. my mind) existed before the formation of the physical object (i.e. my brain), and was lucky not to have “missed the boat”. We think of ourselves as “atomic” — i.e. as incapable of being subdivided into smaller parts, and as having an all-or-nothing existence that can’t emerge gradually from something more inchoate. Such presuppositions are “buried”, and are brought to light by the current sense of having been lucky.

The same sense of perplexity surrounds the so-called “hard problem of consciousness”. We find it relatively easy to imagine how some other agent — even an intelligent robot — might do all of the things that conscious persons do, yet we find it hard to accept that “I happen to be one of those things, doing what those things do” (as we point to a functioning brain). This is not a problem for science — it’s a distinctly philosophical problem of personal identity. The deficit is not one of knowledge so much as of the imagination. We find it hard to imagine that we are one and the same thing as a physical brain, wondering how “it came to be itself rather than something else”. If that isn’t a downright mistaken activity, it’s at least playful, like a cat chasing its own tail, imagining a part of itself belongs to something else.

The vague idea that “atomic” human selves are “queued up waiting to be conceived” also contributes to bad science. For example, attitudes to the extinction of our own species reveal that we treat non-birth as something like being “deprived” of birth, which is comparable to death. But this is a mistake. All individuals inevitably die, and all species inevitably come to an end, but these are entirely different. The supposition that they are similar misinforms much current thinking on ecology and catastrophism about climate change.

A Slate article available here discusses the question whether humans are monogamous. It’s worth reading as an example of how laughably bad evolutionary psychology can be. Instead of looking at what humans do and what most of us are most interested in, it begins by considering the human penis and wondering which ape penises the human penis resembles most.

…Which reminds me of an old philosophical joke: “My uncle was almost US President – he was skipper of PT 108!” This is funny, because during the Second World War Jack Kennedy was skipper of the patrol boat PT 109. Obviously, the proximity to 109 of the number of the patrol boat you’re the skipper of is no measure of how close you are to becoming President of the US. It assumes a mistaken dimension of similarity.

How would this sort of thinking work in biology? It might emerge in thoughts such as the following: bonobos live in the Congo, and they’re not monogamous; so the humans who live in the Congo aren’t monogamous either. Fail – where you live has nothing to do with how you normally reproduce. Nor is it any better to appeal to genetic proximity between species: species diverge because they occupy different environmental niches, adopt different strategies for reproduction, and so on. Small genetic differences often accompany large differences in lifestyle. For example, Galapagos finches are very closely related to each other, but they eat a wide variety of different foods, and thus have strikingly different ways of life. These differences were essential for their survival, and explain how they diverged in the first place. Similarly, although most non-human apes are not monogamous, some non-human apes are. The fact that we humans are a species of ape implies nothing.

The shape or size of of the human penis is probably entirely irrelevant to the question whether humans are monogamous. The human head is unusually large: that makes unusual demands on the human birth canal, and that in turn makes unusual demands on the human penis. Of course the human penis differs from that of other apes, just as our heads differ from the heads of other apes. No doubt other ape penises differ from each other, like other ape heads differ from each other.

The size of the human head actually does have some bearing on the question of human monogamy. Big brains are costly to maintain and to grow, both in terms of metabolism and learning. If humans who have healthy, well-fed brains, and skilled, knowledgeable minds do better – not just better at survival but better at getting chosen in the tricky game of sexual selection – we should expect to see whichever reproductive arrangements most effectively make them better. I think such arrangements are those of monogamy. The reproductive task of humans is in some ways similar to that of flying birds, which have to convert an egg into a flight-worthy fledgling in a very limited time “window” set by the length of the season. Their usual strategy is monogamy, with both parents involved, although of course monogamy is never perfect because cheating occurs in all monogamous species. Even where cheating occurs, successful reproduction normally makes demands on two adults rather than just one.

But the real clincher is simple observation: wherever we look, at whatever point in history, humans are and have always been intensely interested in love and marriage. Human attachment is more than an interest: it looks more like an obsession when we compare humans to most other animals such as non-monogamous apes. Love is the main theme of all forms of human art. Long-term partnerships are sought everywhere, from classified ads in newspapers to newer forms of “social media”.

The Slate article referred to above tells us that “According to anthropologists, only 1 in 6 societies enforces monogamy as a rule.” What they probably mean is that only 1 in 6 societies disallows divorce as a matter of fanatical adherence to law or scripture. But accepting that marriages often break down is different from not recognizing marriage or not acknowledging long-term partnership as an institution at all. And all human societies recognize long-term partnerships, as evolutionary biologist Helena Cronin often explains in detail.

There are several reasons why anthropologists and others overlook or seek to downplay the ubiquity of monogamy. Some of them illustrate errors that are philosophically instructive in themselves:

1. Like much “research” in the humanities, anthropologists’ observations are neither repeatable nor inter-subjectively verifiable, and they involve more interpretation than observations within the genuine sciences. Some anthropologists have interpreted their subject matter with such a heavy-handed political agenda or pervasive ideology that their work has become notorious. Margaret Mead’s writings about Samoa are better-known for their errors of interpretation than for what she actually got right.

2. The urge to say that humans are not monogamous had a resurgence with the “free love” movement of the 1960s. In this movement, a subculture of mostly young people hoped to break free from the hidebound and mostly monogamous arrangements that limited the freedom of their parents. But nearly always, the tensions and jealousies so familiar to those in monogamous arrangements re-emerged. It seems we are hard-wired to become attached to a single partner and to demand that that partner remains attached to us in return. This is an ideal, and the reality often falls short of the ideal. When it does fall short it spells trouble, but not the sort of trouble that can be avoided by ignoring or hoping to override human nature. Alas, for many years the academic establishment was populated by more elderly members of the “free love generation” who did just that.

3. Members of the “free love generation” weren’t the only ones to adopt an alternative lifestyle that might be expected to leave monogamy behind. Over the centuries, often out of tragic necessity, both male and female homosexuals had to join a sort of underworld of sexual activity in which legal marriage did not exist. In some places this involved unusual promiscuity, much as it did with heterosexual hippies in the 1960s. But in no place did it not involve long-term love partnerships as well. The urge to join such a partnership seems to belong to those of all sexual preference, even those who would eschew it if it really were such an “unnatural imposition” of human culture.

4. Nowadays, the urge to say that humans are not monogamous is often seen in two superficially opposed corners: feminism and laddism. Both seem to resent any sort of dependency between the sexes, both prefer to think that women don’t need men to help raise children, and for notably different reasons, both prefer to think that mothers shouldn’t depend on the fathers of their children for support. Because “both sides” seem to arrive at the same conclusion, it might seem to be surrounded by an air of consensus. Those who find consensus convincing should look instead at the vast majority of humans who belong to neither of these extremes, and instead agree that the involvement of two parents is the best and most “natural” arrangement for raising children, as well as for growing old in.

5. It is sometimes claimed that institutions like marriage are imposed on humans by human laws, as if nurture overrides human nature, which would otherwise be non-monogamous. But nurture adds detail to innate human capacities and urges rather than opposing or overriding them. Human culture such as our legal system often involves the policing of arrangements that the majority would abide by anyway, in the absence of such laws, as a matter of unforced natural choice. This is true of laws of ownership, and it is just as true of laws concerning marriage and divorce. So the fact that we have laws that seem to “enforce” monogamy – by making special allowances for it – does not detract from its naturalness. It isn’t a “social construct” or something “imposed by society” as an unnatural afterthought.

6. The Slate article cited above says that the question of human monogamy is “complicated”. I think they say this because they assume the concept of monogamy is perfect, like the concept of a perfect circle, and therefore simple. Their concept is too simple for the reality to match it, so the reality ends up looking more complicated than the concept. But that perfect concept is too simple. Some members of all monogamous animal species cheat, and in doing so they do not make their species as a whole any less monogamous compared with alternative reproductive arrangements. The concept of “monogamy” in the claim that “humans are monogamous” should be understood as being analogous to the concept of “round” in the claim that “the Earth is round”. We say the Earth is round because it’s shaped like a ball rather than flat. We don’t say it’s round because we think it’s a perfect sphere. Analogously, humans are monogamous because human children normally need the care and attentions of two parents rather than one, and new children are born before older children have reached adulthood. So normally the same parents are involved with each successive child. This involves a pair bond that in favorable circumstances lasts for life. It doesn’t matter much that it often doesn’t actually last for life: an animal that dies before it reaches its species’ life expectancy is no less a member of that species for dying young.

Perhaps it is because a faithful lifelong partnership is not often achieved among humans that monogamy is often treated as an ideal. But it should be understood as a moral or personal ideal rather than as a conceptual ideal like a perfect sphere. But it is also a biological reality, like “good health”. Once we grasp that all the other animals we unhesitatingly call monogamous have the same problems and shortcomings as ourselves, we see that ours too is a monogamous species. It’s simple really.

Various sorts of morally reprehensible behaviour exist in humans because they confer biological advantages on the agents. Similar sorts of behaviour exist in animals.

For example, male lions tend to kill cubs that they did not sire. In doing so, they “make room” for their own cubs – “room” that consists of scarce resources such as the mother’s care, and shared food and protection of the rest of the pride. By killing the offspring of others, they give life to their own offspring – which carry genes for infanticidal behaviour and thus ensure that it continues.

Or again, mallard ducks are notorious rapists. This behaviour continues from one generation to the next, again for obvious evolutionary reasons.

Like male ducks, men are potential rapists, and for the same evolutionary reasons. Rapists who are accused of rape generally do not admit to rape – so they’re liars as well as rapists. And again, they’re liars for evolutionary reasons. Rapists who don’t admit to rape are more likely to rape again and pass their genes on so that the raping and lying continues from one generation to the next. Their behaviour is morally reprehensible, but its biological causes are well-understood.

Women’s behaviour can also be morally reprehensible, as well as being well-understood biologically. For example, women sometimes commit infanticide – not just by killing other women’s children to make more room for their own children, as men do, but also by sometimes killing their own children. The second sort of behaviour makes more room for later children of their own at a more opportune time, such as when they can hope for better provisioning.

Like men, women are prone to mendacity in circumstances where it is biologically advantageous to tell lies. These circumstances need not be as dramatic as rape, although lack of consent of one party or another (such as a cuckolded husband) is always involved. “Ordinary” extra-marital “cheating” can be biologically advantageous to those who can get away with it by lying successfully. Although the respective advantages can differ slightly, cheating can enable both sexes to produce a larger number of offspring and/or offspring with a wider variety. But secrecy is essential – mendacity evolved with the cheating behaviour. Through cuckoldry, both men and women can raise offspring provisioned by victims of mendacity – those who have been duped into thinking they are provisioning their own offspring. This is common among monogamous animals, and humans are no exception.

Intelligent and just law-making must take account of the biological roots of these sorts of mendacity. For example, if a woman accuses a man of rape, no decent, just law would simply “take the man’s word for it” if he denies it. (Nor would it simply take the word of the woman who asserts it.) Similarly, if a woman claims a man is the father of her child, we shouldn’t simply take her word for it, as it might be an attempt to dupe him into provisioning someone else’s offspring. To overlook this possibility is to court injustice.

In principle I welcome the suggestion that a child’s birth certificate should carry the names of both mother and father. But the law must ensure that the name of the father is decided by more than the mother’s say-so.

Some people think that the human condition is essentially one of “irrationality” – that we are all cognitively flawed in a deep and irredeemable sort of way.

I don’t think we’re quite as bad as that. I have three sorts of reasons for thinking we’re not as irrational as pessimists think. But alas, I also have two sorts of reasons for thinking we’re still far from perfect.

My first sort of reason to think we’re not all that irrational stems from agreement with Hume that reason is “the slave of the passions, and can never pretend to any other office than to serve and obey them”. This means that “the heart wants what the heart wants”, and “the head” works out how best to achieve it. And only “the head” is capable of being rational or irrational. For example, smokers are often treated as if they were making a mistake. But according to Hume’s way of thinking, they have simply made an alternative lifestyle choice. They value their health less highly than non-smokers, of course, but that can’t be regarded as a case of irrationality. They’re doing what they want to do, and wants aren’t capable of being irrational.

By dividing the activities of the mind into volition and cognition, this approach effectively insulates the first “half” of them from rational criticism. Rationality doesn’t apply to the having of desires as it does apply to the formation of beliefs.

My second sort of reason to think we aren’t all that irrational draws on the ideas of recent philosophers like Dennett and Davidson. According to their variety of pragmatism, the content of a belief is a matter of interpretation. That is, a belief is about whatever a fully-informed interpreter would say it is about. To see how this works, consider an ultra-simple rudimentary agent such as a thermostat. Suppose it keeps the room at a steady 70 degrees. Then, as interpreters, we would say its (rudimentary) goal or “desire” is to keep the room at 70 degrees, and that its (rudimentary) “belief” is that the room is either hot enough or else not hot enough, depending on whether or not its bimetal strip is distorted enough to break the circuit to the heater. Even if the bimetal strip is permanently bent with age, and the dial “says” the thermostat should be keeping the room at 80 rather than 70 degrees, what counts is not what the dial “says” but what it actually does.

This is relevant, because much human irrationality is supposed to emerge when belief and action have become “decoupled”. For example, suppose someone looks up at the sky and says, “oh dear – I think it’s going to snow!” But then he puts on Wellington boots and a raincoat, grabs an umbrella, and so on. On the face of it, that seems like irrational behaviour. But let’s look more closely. If his behaviour is consistent with someone who thinks it is going to rain rather than snow, interpretation leads us to assign the belief that it is going to rain rather the belief that it is going to snow. We simply override his own report of what he thinks. He is probably using the word ‘snow’ in an aberrant way, much as the thermostat’s dial “said” – inaccurately – that its goal was to keep the room at 80 degrees. That is a linguistic misunderstanding rather than a case of irrational action or irrational belief. We are obliged to re-interpret the contents of the agent’s mind so as to maximize the rationality of his actions and beliefs, and when we do so, we find far less “decoupling” than we originally feared.

My third sort of reason to think we aren’t all that irrational comes from evolutionary theory. Like other creatures, we evolved to survive at least to the point where we have successfully reared offspring. This entails that as far as everyday beliefs that guide behaviour are concerned, most are probably true or approximately true. It also entails that they can’t contradict each other very much. Imagining a creature with a lot of false or contradictory beliefs is like imagining a creature that walks into closed doors, doesn’t avoid cliff edges, and so on. And that is to imagine a creature that can’t survive long enough to reproduce, like a soluble fish, as Dennett remarked.

So much for three sorts of reason for thinking we’re not as irrational as we might fear. All of them are consistent we the idea that we are “survival machines” for our genes. For that, we have to be reasonably efficient vehicles for their passage into future generations, and for that, we have to do our cognitive work reasonably well. I see the pessimistic alternative as being inspired by more traditional “takes” on the human condition. The idea that we are cursed from birth with the madness of irrationality is reminiscent of the doctrine of Original Sin. The idea that our minds are not subject to fine-tuning through constant interaction with the physical world is reminiscent of mind-body dualism. The idea that cognitively speaking we are in a place of “darkness” is reminiscent of radical Cartesian scepticism.

We can avoid those sources of pessimism by moving beyond our religious traditions. But the alternative evolutionary perspective brings its own brands of pessimism with it. I can see two sorts of reason for thinking we aren’t quite as rational as we might hope.

The first stems from the fact that we are a social animal. Much of our thought is guided by moral concerns, and by empathy for members of our own group (which is often not at all “moral” in any obvious sense, as it discriminates against members of other groups).

There is strong selective pressure against the sort of false beliefs that would lead us to walk into closed doors or over the edge of cliffs. But the selective pressure against false beliefs of a more “theoretical” sort – such as beliefs in religion, history, or even science – is much weaker. In fact any selective pressure here is probably negative – that is, the social advantage of having similar beliefs to others outweighs any disadvantage attached to their being false. The positive effects on our gene-propagating potential of having the same beliefs as others spring from the way they help to identify which group we belong to, which hymn sheet we’re singing from, and where our allegiances lie. And above all whom we can turn to for help if we need it. Truth here takes a second place to reciprocal altruism.

If we want to have true beliefs of this theoretical sort, and practically everyone who professes to have a “scientific” outlook does, then we are going to have to control our urge to “belong”. Such urges militate against truth, and given a truth-oriented outlook they are irrational.

I don’t see much effort made to control these “social” urges. Most current academic philosophers’ energies seem to be expended more on saying popular, agreeable things and avoiding any real controversy. Wider attitudes to “denialists” of one sort or another seem not to have advanced one inch beyond the opprobrium traditionally heaped on heretics, infidels, apostates and blasphemers. Just adopting a new word for non-co-religionists does not auger well for our pursuit of truth or for human rationality.

The second sort of reason to think we aren’t as rational as we’d hope has to do with sexual selection. In sexual selection, members of the selected sex exhibit dangerous or expensive ornaments and engage in self-destructive or wasteful behaviour in order to send a “costly signal”. A signal has to be costly to be convincing – hence the length, inconvenience and danger of owning a peacock’s tail.

In humans, as in monogamous birds, each sex is subject to selection by the other sex. Both men and women bear the marks of this process of selection. For example, permanent and cumbersome human breasts signal fertility and youth. Tribalism and earning power signal strength and intelligence. But being well-endowed or getting paid a lot of money doesn’t make anyone more truthful or more competent in their pursuit of truth.

The combination of sociality and sexual selection in humans has given rise to some bizarre social arrangements, including – in some parts of the world and much of history – the segregation of the sexes. In these arrangements women are in effect incarcerated, and men in effect spend their days slapping each other’s asses with wet towels in changing rooms.

None of that is conducive to truth or to human freedom. If we primarily value truth or freedom, promoting the opposite may be a typically wasteful self-handicapping “signal” – but it’s irrational.

So much for human irrationality as I see it. Shall we say: three out of five ain’t bad?

The concept of belief is really very simple. You believe something when you think it’s true. The “something” you believe – the “it” that you think is true – is its content, which can be expressed as a declarative sentence. That’s how we usually ascribe beliefs, as in “Bill thinks Paris is the capital of France”, where the embedded sentence ‘Paris is the capital of France’ is true in the same range of situations as Bill’s belief.

Animals obviously have beliefs, even though they don’t have language. So those embedded sentences are generally not literally inside the head of the animals whose beliefs they correspond to. Rather, the belief plays a similar role in the animal’s mental economy as the sentence plays in the language’s inferential economy. The role of the sentence in the language – what it would be true of, what it implies, what implies it, and so on – mimics the role of the belief in the animal’s belief-system – such as what the animal infers from it.

Although the concept of belief is simpler than the concept of knowledge, we seem to acquire it later in life. There’s a reason for that. Having knowledge is the normal state of any perceiving mind with respect to the world. Evolution shaped brains, afferent neurons, sense organs, etc. so that minds would have knowledge. So when we humans begin to talk as infants, we tend to talk about the most familiar normal situations of agents knowing things about the world they live in.

Only after we have acquired a working concept of knowledge are we able to abstract from it to acquire the concept of belief (and many do not get that far). An item of knowledge is a true belief sustained by reliable processes. We sculpt our (simple) concept of belief by chipping some bits off the larger stone of our (less simple) concept of knowledge. We do it by “bracketing” or suspending in our imagination the condition that it be true, and/or the condition that it be sustained by reliable processes. These extra conditions typically depend on states of affairs outside the head of the knower – truth depends on the subject matter of the belief, and reliability depends on information channels such as sense organs. Only after we have isolated the component of knowledge that lies wholly inside the head do we finally arrive at the concept of belief.

There are some legitimate reasons why beliefs are of special interest to us. But there is at least one illegitimate reason: the ubiquitous Cartesian view of the mind as being “cut off” in a problematic way from the “outside world”, so that we are “not entitled” to talk about anything beyond “the inner”. Thus begins an unhealthy preoccupation with certainty and with “justification” – in other words, with internal guarantees or checks on the supposed goodness of our beliefs.

Internalism has done untold damage to epistemology in particular, and to philosophy in general. That’s a misfortune, but it’s one that mostly only academics have to live with. However, internalism has also done untold damage to the lives of ordinary people, in its application to volition. I’ll try to explain.

The concept of desire is as simple as that of belief, and our acquisition of it mirrors that of belief. We start off with successful intention rather than knowledge. Successful intention is the normal outcome of any act. Most of the time when we say “he did X”, we mean he meant to achieve X when he acted, and he actually succeeded.

I mentioned above that evolution shaped brains to have knowledge. But that knowledge serves an even more fundamental evolution-given purpose: to promote the proliferation of our genes in future generations. Evolution shaped brains, efferent motor neurons, muscles, etc. for achieving goals. So when we first begin to talk, we talk about the most familiar normal situation of agents achieving goals in the world in which they act.

Only after we have acquired a working concept of successful intention are we able to abstract from it to acquire the concept of desire (and, strange as it may sound, I would argue that many do not get that far). A successful intention is a desire that reaches its goal by means of reliable processes. We acquire the concept of desire by “bracketing” or suspending in our imagination the condition that it reaches its goal and/or the condition that it does so through reliable processes. These extra conditions typically depend on states of affairs outside the head of the knower – success depends on the object of the desire (a state of affairs) being realised, and reliability depends on working machinery such as motor neurons, muscles and limbs. Only after we have isolated the component of successful intention that lies wholly inside the head do we finally arrive at the concept of desire.

As with belief, there are some legitimate reasons for being interested in desire as opposed to successful intention. But as with belief, the Cartesian reason is illegitimate. The idea that our minds are “cut off” in a problematic way from the world in which we act narrows our focus, so that it settles on experienced wishes. There is real danger in this – not just for academics but for the way ordinary people live their lives. We are liable to think of a strong desire as a vividly-experienced wish instead of one that emerges in decisive action. And we may mistake fantasy for actual desire, even though we often fantasise about things we have an extremely powerful aversion to, such as rape. It is that sort of confusion that leads me to say many people never get as far as having a clear concept of desire. By confusing it with vividness of experience, they make a similar mistake to those who suppose the subjective feeling of certainty is a guarantee of truth.

The perspective of traditional epistemology is to look from the inside outwards. From that perspective, the concept of belief looks more primitive than the concept of knowledge, and it looks as if we can treat beliefs that have the extra ingredient of “justification” as making it over a hurdle to become knowledge. The same perspective supposes that intention is “like desire, only stronger”. I recommend an alternative perspective, which takes desire to be more like an attenuated form of intention. Instead of expanding our concepts of belief and desire to include the concepts of knowledge and intention, we have to contract our concepts of knowledge and intention till all we have are concepts of belief and desire.

I think this has a real bearing on how we live our lives, because so often we appeal to internal “feelings” when making judgements about what we really desire. For example, young parents are harsh on themselves if they do not feel a strong sense of attachment to a newborn baby. Lovers misread jealousy as a wholly “negative” emotion. Spouses mistakenly think they have fallen out of love if they have grown accustomed to each other. Terrorists deem their own actions to be morally right if their experienced urge is to do good.

Thoughts such as those lead people to make bad decisions in life.

As we discuss the possible introduction of gay marriage, we often hear expressions of the “enlightened” view that marriage is a “man-made” institution. I’m 100% in favour of gay marriage, but I can’t agree with that view. Human culture is just an extension of human nature, and it is a mistake to see aspects of culture as working “against nature”. Culture instead adds detail to innate biological urges and abilities. For example, human languages differ from each other because they developed along different lines. In other words, they were so developed by the people who spoke them, and in that sense they were “man-made”. But the fact that every human speaks some language or other indicates that language use is innate. It is not “artificially imposed” on human nature by human culture as an optional extra. Marriage isn’t artificially imposed on human nature by human culture either. As with language, all human cultures seem to have some form or other of marriage, as indeed do some other animals such as monogamous birds that observe public courtship rituals. This indicates that marriage serves a biological “purpose”, like erotic love itself.

The biological purpose of erotic love is committed parenthood in monogamous species. These are species in which offspring are a big investment for both parents, so big an investment that both parents have to be firmly committed to their role as parents and bonded to each other as a pair. Public “ceremonies” seem to add “cement” to such pair bonds. The extra “cement” is advantageous in species whose offspring represent an unusually large investment, such as humans. There’s a selective pressure for a more durable bond, because monogamy is always threatened by infidelity, which also serves a biological purpose (although a slightly different one for each sex). No species is perfectly monogamous in that none of its members cheat, although in many species some pairs are perfectly monogamous in that neither member ever cheats. At the level of entire species, monogamy is always less than perfect, even among those whose fidelity is legendary such as swans. Thus the presence of cheating among some members of a species does not diminish the claim of the species as a whole to be a monogamous one.

If love and the institution of marriage are “natural” for humans because we are a monogamous species, changing them or common perceptions of them might be more difficult than we think. It doesn’t matter what other people think about love, because that only exists between two people. Homosexual love obviously exists and always did exist regardless of homophobic attitudes of the surrounding culture. But marriage is another matter. For it to exist in the proper sense of the word, it has to be widely recognized as marriage by the surrounding culture, and I’m not entirely convinced that’s possible with homosexual marriage just yet. I wish it were possible, but I’m being realistic.

Since homosexual sex cannot result in parenthood, it is not surprising that many people see homosexual love and marriage as “not quite the real thing”, as biologically secondary to heterosexual love and marriage. Of course we must not draw any “oughts” from that unpalatable fact, but I think we should at least acknowledge it as a fact.

As I write, proponents and opponents of gay marriage are being urged to sign online petitions for or against. The “anti” vote currently stands at almost ten times the “pro” vote. If those numbers reliably reflect popular opinion, that would be disappointing, but hardly surprising, as it simply reflects human biology. It would be disappointing, because it probably means that for now, even if gay marriage were made possible in the full legal sense, it would not be widely recognized as marriage.

This isn’t always a sign of homophobia. Humans are intensely interested in erotic love, for the obvious biological reason that human children are a sort of “life sentence”. A single human childhood is easily the longest and most resource-consuming project in the living world, so the choice of who to marry and/or have children with is a biologically momentous decision – it’s literally a matter of life and death, not only for the children but also for the occasional suicidal abandoned spouse or murderous cuckolded non-parent. Erotic love is the central preoccupation of human art. We are all fascinated by the many variations on the theme of love, and we all speculate about how well or badly the old, the young, the rich, the famous, above all the different will fare in the dangerous game of marriage.

If we’re honest about it, we all wonder how well or badly things will turn out where there are big age differences, religious differences, racial differences, or differences in social class. And we see the importance of sameness as well. Most of us see various strengths and weaknesses in the various possible similarities and differences. For example, most of us are ready to accept a big age difference if the man is older than the woman, but raise an eyebrow if the man is younger than the woman – especially if the man is poorer than the woman.

If we’re honest about it, most of us realise that marriage between a man and a woman can be hard going, but the long trek unto death is made slightly easier by a sort of complementarity between them. If the man is a boor and the woman is a shy accepting little mouse, that is horrible – but at least their minds are made for each other like sex organs. If the man is a hen-pecked weed and the woman is a harridan, that is not quite so bad, but again: at least they are made for each other.

This brings us to the crux of the problem: Why are so many of us apparently not yet ready to recognize marriage between two people of the same sex? – I think we see (or think we see) a lack of complementarity between the people involved. I for one do not see any such complementarity, bad and all as heterosexual marriages often are, and I would be amazed if the mean length of non-married homosexual partnerships was anything like as long as the mean length of non-married heterosexual partnerships. That is one of the reasons I support homosexual marriage: it might add “cement” to homosexual partnerships in the same way as it does to heterosexual partnerships.

No doubt what I’ve written here will strike many as homophobic. And I am a heterosexual, which does not portend well. But I have had unusually intimate relationships with homosexual men and women for much of my adult life, through one accident of fate or another. Much of what I know about evolutionary biology I learned from the greatest – and incidentally homosexual – philosopher of biology there has ever been. I think all of them would agree with what I have just written, and all have expressed views very similar to my own.