Monthly Archives: July 2013

The Case of the Falling Fat Man

by Tim Harding

Is it justified to kill an innocent threat in defence of oneself or others?

An ‘Innocent Threat’ is a person who poses an imminent threat your life, but who is not the originating cause of that threat, as in the ‘Falling Fat Man’ case hypothesised by Thomson (see below).  Some philosophers such Thomson argue that it is morally permissible to kill an Innocent Threat in self-defence (Thomson, 1991); whilst other philosophers such as Otsuka argue that it is not permissible (Otsuka, 1994).  In this essay, I intend to argue that it is justified to kill an innocent threat in defence of oneself or others, but on different grounds to those used by Thomson.  My grounds are (1) the traditional conditions for justification of self-defence; (2) the Doctrine of Double Effect (which is rejected by Thomson within this context); and (3) utilitarianism, in cases of defending more than one person.

In her 1991 paper on ‘Self-Defense’, Thomson provides three hypothetical cases in which she thinks it is morally permissible for you to kill a person in self-defence (‘Yes cases’); and three cases in which she thinks it is not permissible (‘No cases’).  These cases are:

      Yes cases        No cases
  • Villainous Aggressor
  • Innocent Aggressor
  • Innocent Threat
  • Substitution-of-a-Bystander
  • Use-of-a-Bystander
  • Riding-Roughshod-over-a-Bystander

A Villainous Aggressor intends to kill you, as in the case of a truck driver deliberately trying to run you over; whereas an Innocent Aggressor is not to blame for his aggression (for example, if he or she is insane).

An Innocent Threat does not intend to kill you, but will nevertheless do so unless you kill him or her.  For example, in Thomson’s Falling Fat Man case, you are lying in the sun on the balcony of your apartment and a fat man pushed by another person is falling towards you.  The only way you can prevent him falling on you and killing you is by moving an awning, which will deflect his fall on to the road below, where he will die.  If you do not deflect his fall in this way, your body will cushion his fall and he will live (but you will die).  The important point is that not only is the Falling Fat Man innocent, but he is not the cause of his fall towards you (Thomson, 1991:287).


Thomson argues that there is no moral difference between the three ‘Yes cases’ – in each case the threat will kill you if you do not kill him or her.  She says that, other things being equal, every person Y has a right against X that X not kill Y.  In summary, she concludes that the threats in the ‘Yes cases’ will violate your rights that they not kill you, and therefore they lack rights that you not kill them (Thomson, 1991:300-305).

In contrast, bystanders are not threats – they are not causally involved in the imminent threat to your life.  Thomson concludes that bystanders do have rights not to be killed and therefore may not be killed in self-defence against a threat not caused by the bystander (Thomson 1991: 298-299).

On the other hand, in his 1994 paper Otsuka argues that there is no moral difference between an Innocent Threat and a bystander.  He thinks that it is never justified to kill innocents in self-defence.  It is morally impermissible to kill a bystander and therefore it is also impermissible to kill an Innocent Threat.[1]

The implication of Otsuka’s theory that you are morally obliged to lie back and let the Fat Man fall on you is counter-intuitive and likely to be rejected by most people.  Appeals to intuition and public opinion are, of course, not philosophical arguments, but I think they can sometimes act as a ‘reality check’ to indicate that there might be something inadequate with a moral theory like Otsuka’s; and that alternative approaches need to be considered.

For a start, Otsuka’s theory conflicts with the Hobbesian account of self-defence that if one will die unless one does X, then one has a right to do X.  However, this right needs to be limited in some way.

The traditional conditions for justification of self-defence are that (a) the threat must be imminent; (b) the defensive violence must be necessary; and (c) the force used must be proportionate to the threat.  I would argue that conditions (a) and (b) are an intrinsic component of the ‘Falling Fat Man’ case.  The proportionality condition (c) is demonstrated in DDE criterion (1) below.

The Doctrine of Double Effect (DDE) states that we may do what will cause a bad outcome in order to cause a good outcome if and only if (1) the good is in appropriate proportion to the bad and (2) we do not intend the bad outcome as our means to the good outcome (Thomson, 1991:292).  For example, it is morally permissible to give a terminally ill cancer patient enough morphine to relieve excruciating pain even if we know that this dose will kill the patient.  Thomson rejects the application of the DDE to the cases under discussion on the grounds that a person’s intentions are morally irrelevant (Thomson, 1991:293-296).

My view is that intentions are relevant to the morality of killing in general and to the killing of Innocent Threats in particular.  For example, in general terms, the essential moral difference (leaving aside the legal difference) between a murder and a manslaughter charge is one of intent.  All other facts of the case may be identical.

I think that Innocent Threats meet the criteria for the application of the DDE, as follows:

(1)  the good is in appropriate proportion to the bad because either you will be killed or the Innocent Threat will be killed.  Either way, one person will die; and

(2)  your intent in defending yourself from an Innocent Threat (for example, by shielding yourself from the Falling Fat Man) is merely to save your own life.  The death of the Falling Fat Man is an unavoidable consequence of the necessary action you take to save your life, rather than the purpose of your action.

The DDE can also apply to the defence of others – the above criteria could also be met in such cases.  In cases where more than one person is being defended, the good may even outweigh the bad.

Utilitarianism is of little assistance in the Falling Fat Man case.  Both you and the fat man are likely to have a preference to live.  Either way, one person will die.  The life of one of you may be more valuable to the community than the other and therefore have better consequences from being saved, but that is an assessment you are unable to make when a fat man is about to fall on you!  However, in other cases Utilitarianism may be relevant to the defence of more than one other person, on the grounds that saving more than one life would be a better consequence than saving only one life.

In conclusion, I think it is justified to kill an Innocent Threat in defence of oneself or others on the grounds of the traditional conditions for self-defence; the Doctrine of Double Effect; and utilitarianism in cases of defending more than one person.


 Otsuka, M. (1994) ‘Killing the Innocent in Self-Defense’ Philosophy and Public Affairs, Vol. 23, No. 1 (Winter, 1994), pp. 74-94.

Thomson, J. (1991) ‘Self-Defense’ Philosophy and Public Affairs, Vol. 20, No. 4 (Autumn, 1991), pp. 283-310.

[1] Otsuka also argues that it is morally impermissible to kill an Innocent Aggressor, but that issue is outside the scope of this essay topic.

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Preference failure

by Tim Harding

According to economists, preference failure occurs when someone acts contrary to their own interests or intentions. Prime examples are addictions, such as to smoking, alcohol, other drugs or to gambling which can often result in ill-health, financial ruin and/or death. Addicts are usually aware of the harmful consequences of their actions, but by definition they are unable to break their bad habits. So the problem here is not information failure – it is a form of irrationality, where short-term pleasure overrides long-term welfare(1).

Less obvious forms of preference failure occur when someone may believe that they are doing the right thing, but their actions are counter-productive to their intentions.

For example, a survey by Monash University in 2005 found that 22 per cent of people said they sometimes fed a cat that did not belong to them (2). Some people may feel they are being kind because they know that stray cats suffer from starvation, disease and injuries from fights with other cats. But because they are ‘unowned’, stray cats are deprived of the regular meals, shelter, grooming and veterinary care that owned cats receive. Feeding stray cats provides a short-term ‘feel good factor’ that acts against the long-term welfare of the cats. Being a stray cat is not a sustainable lifestyle, with an average life-expectancy of only 3 years. So feeding them actually perpetuates the misery of these poor animals (and their kittens), which on a rational basis should either be adopted as pets or euthanased.

An adverse side-effect is that stray cats are also more likely to kill birds, possums and other native animals than owned cats, at least some of which are kept indoors overnight. The kindest thing to do for a stray cat would be to ‘adopt’ it (but have it checked for a microchip by a vet first). If this is not possible, contact an animal welfare organisation such as the RSPCA or the Cat Protection Society.

Preference failure is not usually a fallacy of deductive logic, in the sense of drawing an invalid conclusion from stated premises. It is more likely to be an instance of invalid inductive reasoning, where the evidence has insufficient inductive strength to justify the behaviour.


1. Abelson, P. (2008) Public Economics – Principles and Practice. McGraw-Hill, North Ryde.


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What is logic?

The word ‘logic‘ is not easy to define, because it has slightly different meanings in various applications ranging from philosophy, to mathematics to computer science. In philosophy, logic’s main concern is with the validity or cogency of arguments. The essential difference between informal logic and formal logic is that informal logic uses natural language, whereas formal logic (also known as symbolic logic) is more complex and uses mathematical symbols to overcome the frequent ambiguity or imprecision of natural language.

So what is an argument? In everyday life, we use the word ‘argument’ to mean a verbal dispute or disagreement (which is actually a clash between two or more arguments put forward by different people). This is not the way this word is usually used in philosophical logic, where arguments are those statements a person makes in the attempt to convince someone of something, or present reasons for accepting a given conclusion. In this sense, an argument consist of statements or propositions, called its premises, from which a conclusion is claimed to follow (in the case of a deductive argument) or be inferred (in the case of an inductive argument). Deductive conclusions usually begin with a word like ‘therefore’, ‘thus’, ‘so’ or ‘it follows that’.

A good argument is one that has two virtues: good form and all true premises. Arguments can be either deductiveinductive  or abductive. A deductive argument with valid form and true premises is said to be sound. An inductive argument based on strong evidence is said to be cogent. The term ‘good argument’ covers all three of these types of arguments.

Deductive arguments

A valid argument is a deductive argument where the conclusion necessarily follows from the premises, because of the logical structure of the argument. That is, if the premises are true, then the conclusion must also be true. Conversely, an invalid argument is one where the conclusion does not logically follow from the premises. However, the validity or invalidity of arguments must be clearly distinguished from the truth or falsity of its premises. It is possible for the conclusion of a valid argument to be true, even though one or more of its premises are false. For example, consider the following argument:

Premise 1: Napoleon was German
Premise 2: All Germans are Europeans
Conclusion: Therefore, Napoleon was European

The conclusion that Napoleon was European is true, even though Premise 1 is false. This argument is valid because of its logical structure, not because its premises and conclusion are all true (which they are not). Even if the premises and conclusion were all true, it wouldn’t necessarily mean that the argument was valid. If an argument has true premises and its form is valid, then its conclusion must be true.

Deductive logic is essentially about consistency. The rules of logic are not arbitrary, like the rules for a game of chess. They exist to avoid internal contradictions within an argument. For example, if we have an argument with the following premises:

Premise 1: Napoleon was either German or French
Premise 2: Napoleon was not German

The conclusion cannot logically be “Therefore, Napoleon was German” because that would directly contradict Premise 2. So the logical conclusion can only be: “Therefore, Napoleon was French”, not because we know that it happens to be true, but because it is the only possible conclusion if both the premises are true. This is admittedly a simple and self-evident example, but similar reasoning applies to more complex arguments where the rules of logic are not so self-evident. In summary, the rules of logic exist because breaking the rules would entail internal contradictions within the argument.

Inductive arguments

An inductive argument is one where the premises seek to supply strong evidence for (not absolute proof of) the truth of the conclusion. While the conclusion of a sound deductive argument is supposed to be certain, the conclusion of a cogent inductive argument is supposed to be probable, based upon the evidence given. An example of an inductive argument is: 

Premise 1: Almost all people are taller than 26 inches
Premise 2: George is a person
Conclusion: Therefore, George is almost certainly taller than 26 inches

Whilst an inductive argument based on strong evidence can be cogent, there is some dispute amongst philosophers as to the reliability of induction as a scientific method. For example, by the problem of induction, no number of confirming observations can verify a universal generalization, such as ‘All swans are white’, yet it is logically possible to falsify it by observing a single black swan.

Abductive arguments

Abduction may be described as an “inference to the best explanation”, and whilst not as reliable as deduction or induction, it can still be a useful form of reasoning. For example, a typical abductive reasoning process used by doctors in diagnosis might be: “this set of symptoms could be caused by illnesses X, Y or Z. If I ask some more questions or conduct some tests I can rule out X and Y, so it must be Z.

Incidentally, the doctor is the one who is doing the abduction here, not the patient. By accepting the doctor’s diagnosis, the patient is using inductive reasoning that the doctor has a sufficiently high probability of being right that it is rational to accept the diagnosis. This is actually an acceptable form of the Argument from Authority (only the deductive form is fallacious).


Hodges, W. (1977) Logic – an introduction to elementary logic (2nd ed. 2001) Penguin, London.
Lemmon, E.J. (1987) Beginning Logic. Hackett Publishing Company, Indianapolis.

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