The evidence that should unsettle you about responsibility is not about the half-second before a movement; it is about where your character came from, and none of it was chosen.
The previous lesson concluded that the famous timing experiments refute a picture of the will that few defenders of free will hold. This lesson assembles the material that does bear on the question, then states the argument that turns it into a conclusion. The argument is a priori and does not strictly need the evidence, but the evidence is what makes it impossible to shrug off.
Constitutive luck
Thomas Nagel and Bernard Williams gave the problem its name in a joint symposium in 1976, published soon after as two essays called "Moral Luck". Nagel distinguished four kinds, and the taxonomy is worth having.
Resultant luck concerns how things turn out: two equally reckless drivers, one of whom meets a child in the road. Circumstantial luck concerns the situations you happen to face: an ordinary German in 1935 was tested in a way an ordinary Argentine was not. Constitutive luck concerns the kind of person you are, your temperament, capacities and inclinations. Causal luck is the free will problem itself, the luck of being determined by antecedent circumstances.
Nagel's observation is that we officially believe people are assessable only for what is within their control, and that once the four kinds of luck are subtracted almost nothing is left to assess. The area of genuine agency shrinks to an extensionless point. He does not resolve the tension, and the essay is more valuable for refusing to.
Constitutive luck is the one this lesson is about, and it is the one that has acquired numbers.
Heritability, and how to read it
The largest relevant study is a meta-analysis by Tinca Polderman and colleagues, published in 2015, which pooled essentially every twin study published between 1958 and 2012: 2,748 publications, 14,558,903 twin pairs, and 17,804 measured traits. Across all of them the average heritability was 49 percent, and for most trait domains the data were consistent with a simple model in which the resemblance between relatives is due to genetic effects that add up.
The classical method behind those numbers is straightforward enough to do by hand. Identical twins share all their genes, fraternal twins about half, and if both kinds are reared together the shared environment is common to both. Falconer's formula estimates heritability as twice the difference between the two correlations, , and shared environment as . Take the classic figures for IQ from Thomas Bouchard and Matthew McGue's 1981 review, an identical-twin correlation of 0.86 and a fraternal-twin correlation of 0.60. Then and , leaving 0.14 for everything else including measurement error.
Now the qualifications, because heritability is the most misunderstood statistic in the sciences.
Heritability is a property of a population in an environment, not of a person. It says how much of the variation in a trait, in that population, is associated with genetic variation. It does not say that half of your intelligence comes from your genes, which is not a meaningful claim. Change the environment and the number changes: if every child were given identical schooling, the heritability of educational attainment would rise, because the environmental variance that used to contribute would be gone. High heritability does not mean unchangeable, and the standard counterexample is the height gained across the twentieth century by better nutrition in populations where height was always highly heritable.
What the twin literature does support is Eric Turkheimer's three laws, stated in 2000. First, all human behavioural traits are heritable. Second, the effect of being raised in the same family is smaller than the effect of the genes. Third, a substantial portion of the variation is explained by neither, which means by the accumulation of idiosyncratic experiences nobody planned.
Read those three together and the point for our subject is clear. Your dispositions came from your genes, which you did not choose; from your family, which you did not choose; and from a mass of contingent experience you did not select either. There is no fourth category in the data where the self-made part would live.
Example. A trait shows an identical-twin correlation of 0.45 and a fraternal-twin correlation of 0.22. Estimate the heritability and the shared environment component, and say what the second number means.
By Falconer's formula, and , which rounds to zero. Almost half the variation tracks genetic variation, essentially none of it tracks growing up in the same household, and the remaining 54 percent is non-shared environment plus measurement error. That pattern is extremely common for adult personality traits, and it is the one that surprises people: the family that everyone assumes formed them shows up as close to nothing in the variance, once genetic resemblance is accounted for. A negative estimate, incidentally, is a reminder that these are estimates from a model, not measurements of a quantity, and that a small negative value means the model is being pushed slightly past its assumptions.
Now you. Someone objects that if a trait is 50 percent heritable then a person is 50 percent responsible for it at most, and that upbringing accounts for the rest. What has gone wrong?
Answer
Two things. First, the arithmetic of variance does not divide up an individual: heritability partitions differences across a population, so "50 percent of your trait is genetic" is not a statement the statistic can make. Second, and more important for this course, the argument treats the non-genetic part as though it were the free part, when the non-genetic part is upbringing and chance experience, which the person did not select either. Splitting an unchosen character into two unchosen halves does not produce a chosen remainder. That is why the argument later in this lesson does not depend on the numbers at all: it would go through even if heritability were zero.
Situations, and how much they move people
The second body of evidence concerns circumstantial luck. The best known results are old and have been argued over ever since.
Stanley Milgram reported in 1963 that 26 of 40 subjects, 65 percent, continued administering what they believed to be electric shocks up to the maximum 450 volt setting when instructed by an experimenter in a laboratory coat. John Darley and Daniel Batson reported in 1973 that among seminary students walking to give a talk, 63 percent stopped to help a man slumped and groaning in a doorway when they were told they had plenty of time, against 10 percent when told they were already late. The subject of the talk they were about to give, in half the cases the parable of the Good Samaritan, made no significant difference.
These have to be reported with their weaknesses. Gina Perry's archival work published in 2013 showed that Milgram's procedure varied more between subjects than his report suggested, that some subjects disbelieved the setup, and that the headline 65 percent comes from one of many conditions with results ranging from near zero to near total compliance. The Good Samaritan study has a small sample. The broader replication crisis in social psychology has been hard on this literature, and a reader should treat single striking studies as suggestive rather than settled.
What survives is the direction of the effect and its size relative to what people predict. Asked in advance, observers massively underestimate compliance in Milgram-type situations and massively overestimate the effect of the seminarians' beliefs. John Doris's Lack of Character of 2002 drew the philosophical conclusion: the trait-based picture of character, on which a person's honesty or kindness is a stable disposition that predicts behaviour across situations, is not well supported, and behaviour is more situation-dependent than either folk psychology or virtue ethics assumes.
For our purposes the moral is narrow but real. Whatever moves people is often not what they believe is moving them, and the circumstances that do the moving are not chosen.
Example. In the Good Samaritan study, helping fell from 63 percent to 10 percent between the unhurried and hurried conditions. State precisely what that licenses and what it does not.
The ratio is , so a seminarian who was not running late was more than six times as likely to stop. What it licenses is a claim about a difference between groups: an unchosen feature of the situation, being told the time, moved behaviour far more than the content of the talk the subjects were about to give, including for those about to speak on this very parable. What it does not license is any claim about a particular individual. Ten percent of the hurried students did stop, so the situation was not compelling, and the study gives no way to tell whether a given non-stopper would have stopped had he been unhurried. The sample was also small, one condition among several in a single 1973 experiment, so the effect size should be treated as an estimate with wide uncertainty rather than as a constant of human nature.
Now you. Does the situationist evidence excuse the hurried seminarians?
Answer
Not on any theory in this course, and it is worth seeing why not, because the temptation is strong. A compatibilist asks whether the mechanism producing the behaviour responded to reasons, and being in a hurry is itself a reason that the agent weighed, badly; nobody was compelled, and the ten percent who stopped demonstrate that stopping was available. What the evidence does do is undermine a different claim, that behaviour flows from stable character, and therefore undermine the inference from one bad act to a bad person. That has real consequences for how we blame, since much of ordinary blame is an inference about character, and it has almost no consequences for whether the act was culpable. Keeping those two apart is one of the more useful things this material teaches.
When a cause is visible
The third body of evidence is clinical, and it is the most vivid.
In 2003 Jeffrey Burns and Russell Swerdlow reported the case of a 40-year-old man with no prior history who developed an intense interest in child pornography and made advances to his stepdaughter. He was convicted, and on the eve of sentencing complained of headache and was found to have a large tumour in the right orbitofrontal region. It was removed, and the behaviour resolved. Some months later the urges returned; imaging showed the tumour had regrown; a second resection resolved them again. The temporal coupling is about as close to an experiment as clinical medicine gets.
The pattern is old. Phineas Gage's frontal injury in 1848 produced a documented change in temperament. Charles Whitman, who in 1966 killed his wife and his mother and then fourteen more people, most of them shot from a tower at the University of Texas, had written that he suspected something was wrong with his own mind and asked for an autopsy; a glioblastoma was found, and the commission convened by the governor concluded that it might have contributed to his actions. The syndrome of acquired sociopathy after orbitofrontal damage is well described in the neurological literature.
Now the question that makes this philosophy rather than medicine. Nearly everyone's reaction to the tumour case is that responsibility is reduced or removed. Ask why. If the answer is that his behaviour was produced by a physical process he did not choose and could not control, then the same description fits a man whose sadism was produced by a childhood he did not choose and genes he did not select. If the tumour excuses, what exactly is the feature it has that the childhood lacks?
There are answers available, and the best of them is reasons-responsiveness from the compatibilist lesson: the tumour patient's behaviour did not respond to reasons, punishment, or the prospect of losing his family, while an ordinary offender's does. That answer is respectable, it is testable in principle, and it draws the line somewhere other than where causal history lies. Whether it holds is exactly what the manipulation argument disputes.
The Basic Argument
Galen Strawson published the sharpest version of the underlying argument in 1994, and called it the Basic Argument. It runs in five steps and uses no empirical premises at all.
You do what you do, in any situation, because of the way you are. To be truly responsible for what you do, you must therefore be truly responsible for the way you are, at least in certain crucial mental respects. To be truly responsible for the way you are, you must have chosen to be that way. But any such choice must itself have been made for reasons, in the light of principles and preferences you already had, so you must already have been a certain way in order to make it. And to be responsible for that way, you would have had to choose it earlier, which requires an earlier self with its own character, and so on without end.
The regress cannot be completed, so true self-determination is impossible, so true moral responsibility, of the kind that would make punishment deserved in the deepest sense, is impossible. Note the reach of the conclusion. It does not depend on determinism: adding undetermined events to the story gives you a character partly formed by chance rather than by you, which is not an improvement. It is impossible in every possible world, which is why Strawson calls the demand incoherent rather than merely unsatisfied.
Example. Which premise does a compatibilist deny, and how?
The second: that being responsible for what you do requires being responsible for the way you are. Compatibilists hold that responsibility is a matter of how an action is produced now, by a reasons-responsive mechanism the agent owns, and not a matter of the history by which that mechanism came to exist. On this view the demand for self-creation is imported from nowhere and answers to nothing in our practices, which never ask an offender whether he chose his own character. The reply that the Basic Argument's defenders give is that the practices in question involve blame and punishment, that these are supposed to be deserved rather than merely useful, and that desert is precisely what an unchosen character cannot support. That exchange is the whole dispute in two sentences, and it is where the last three lessons of this course go.
Now you. A libertarian says agent causation blocks the regress, because the agent originates the choice rather than making it out of a prior character. Does it work?
Answer
It blocks the regress at a price that has to be stated plainly. If the agent's exercise of causal power is not explained by their prior character, then the choice does not flow from who they are, and the connection between character and action that Hume identified as the ground of blame is severed at exactly the crucial moment. If it is explained by their prior character, the regress restarts, since the character was not chosen. The libertarian's best line is to sit between these, holding that reasons make an exercise of the power intelligible without necessitating it, which is a genuine position and the one the previous lesson examined. What cannot be done is to have both full explanation by character and full origination by the agent, and Strawson's argument is essentially the demonstration that you must choose.
What follows
Nothing in this lesson proves that nobody is responsible for anything. The empirical results establish that our characters have specific, measurable, unchosen causes, which almost everybody already believed; the Basic Argument establishes that a particular demanding conception of responsibility cannot be satisfied, if its second premise is granted.
What the two together do is shift the burden decisively. Anyone who wants to keep robust desert has to say what makes an unchosen but reasons-responsive character sufficient for it. Anyone who wants to abandon desert has to say what happens to blame, resentment, gratitude, punishment and the ordinary business of holding each other to account.
That second question turns out to be the more interesting one, and the most influential paper in the modern literature answers it by refusing the framing of the whole debate. It was written by a different Strawson, in 1962, and it is the next lesson.