Some topics are so difficult you need a way in. The worry is that otherwise the students won’t even understand the kind of question the tutor is trying to give them the answers to. As a student I felt this way for a long time about epistemology, I just could not understand the point of knowledge questions. The problem is not so much the materials themselves, as most students can cope with learning some thing without fully understanding them, but the overall question or approach may be incomprehensible (to that particular student!) so that none of the entire discussion which follows makes sense.

What is it in a nut-shell?

If a topic is obscure find a way to present it so that students really grasp what it is about.



This is a difficult topic as the term ‘personhood’ is in common usage and often used interchangeably with ‘human being’. This causes quite a lot of confusion about why philosophers are even bothering to ask whether a being is a person. Now add to this numerous competing claims about who or what counts as a person and why, and the result is a mess. The solution in this case is to remove the discussion from any frame of reference the students may have so that they are not affected by their preconceptions: no longer a discussion about embryos or animals, but a discussion about aliens. Split your students into small groups and ask them to:

Consider the following scenario: you are walking through the park one morning. Suddenly a really bright light illuminates the sky, you shield your eyes and when you look back what can only be described as an enormous UFO has landed in the middle of the clearing. People run to see what is happening and you are one of the first there. A door opens, a ramp extends and a small green man walks out. Aliens have landed on earth. You now need to decide how to treat them;

  • Should you see if they are edible and if so use them as food from now on?
  • Should you see if their physiology is similar to humans so they can be experimented on to advance medical science and technology?
  • Should you see if they have any amusing/entertaining characteristics that they can perform for our pleasure (perhaps in a zoo or as pets)?
  • Should you see if they have any athletic or sportsmanlike qualities we can put to use for our amusement (perhaps by hunting them or provoking them to fight with each other while we bet on them)?
  • Should they be accorded full citizenship rights, with access to public health, education and the protection of the law?

It is likely that your students will be perplexed by this question and the options available. This is because they are likely to assume that these aliens have comparable moral status to us, rather than beings we consider less morally significant like a variety of animals. If we assume that these aliens are morally significant like fellow humans, we would never consider using them for our pleasure and our benefit. However, it is not clear what status these aliens have or why we should accord them any particular status. It is likely your students will suggest that since the aliens flew through space to get here they are intelligent, therefore they should be accorded respect. If anyone makes this claim concentrate on it; the underlying assumption is that intelligence is significant and it accords you moral rights. Pause here and consider the next part of this exercise.

Another way of putting the question above is to ask whether the aliens are persons.

Let’s define personhood as a technical, ethical term; a person is a being with moral status, someone who is the appropriate object of moral concern (i.e. who should be shown respect, who should not be harmed, whose interests should be protected), a being of moral standing, moral importance. To understand this, consider a chair and a human being. If you want to, you can choose to sit on the chair, paint it pink, break it up, burn it or give it away (assuming it is your chair!). This is not the case with human beings who have value in their own right and should not be treated as objects. However, what is the significant difference between humans and chairs? Why is one a person while the other one clearly isn’t? This question becomes really important when you consider disputed categories, i.e. groups of beings we are not sure about, are they like humans or like chairs? Such beings include our little green men, fetuses and all sorts of different animals. So what kind of characteristic, ability or capacity should we look for in our aliens to decide if they were persons or not?


Your students may have already mentioned intelligence, relating this to the aliens’ evident ability to construct spaceships and travel through space. Other suggestions that may come up (you may need to nudge your students in the right direction) include:

Rationality: now this suggestion is a bit more complicated than mere intelligence. If intelligence refers to matter of IQ, such that your IQ is higher than mine, rationality refers to the ability to reason. This is not a matter of degree for specific individuals, but an ability which characterizes groups of a certain kind. It may also include the ability to be part of a moral community and understand right and wrong: morality is about right and wrong behavior so perhaps we only want to accord moral respect to beings that understand these notions. Note here how a being could be very intelligent without being a moral agent (for example a psychopath who pathologically thinks only of himself but may be a very intelligent (capable and otherwise perceptive) being).

Membership of a social community: membership of a community of relationships, which includes the ability to care for one another and reciprocate this concern.

Membership of the human species. This may sound odd here as it seems to arbitrarily exclude our alien, but it is worth considering as it is often used to exclude animals from personhood.

Sentience and self-awareness. The ability to have interests, i.e. feel pain and pleasure.

Make a list of all the possible characteristics which could qualify a being as a person. Don’t make a decision yet on which one is the best one. Instead consider this list of disputed beings. Take each characteristic in turn and ask “If this were the criterion for personhood would this being qualify?”:  An adult chimpanzee A human egg An amoeba A 13 day old human foetus A 10 month old human child A tree An alien An ecosystem A severely mentally disabled teenage human An adult, mentally competent human being E.g. ask “If intelligence were the criterion for personhood, would an adult chimpanzee qualify?” Alternatively, you could ask each smaller group to consider one characteristic only and apply it to the whole list. They could then report back to the larger group on their findings.


We haven’t yet decided on a criterion for personhood, and this is because this is a very difficult and disputed matter. What we are doing, however, is getting the students to see that who or what qualifies as a person depends on the criterion you use. For example, if you think intelligence matters then human adults and chimpanzees qualify but young human children, the severely mentally ill do not qualify. But if you think that membership of the human species is what matters then adult humans, severely mentally disabled humans and human fetuses qualify but animals and aliens do not. Now it should start becoming clearer that if you use different criteria then different categories of beings qualify as persons. But why is this significant? Because it makes a difference to how we treat these beings. If a being is a person we can’t kill him, cause him harm, experiment on him, use him for our pleasure, use him for profit, etc. If he is not then perhaps we can. So now we get to the difficult bit…which one of these criteria is the correct one? Which capacity, characteristic or ability must beings have in order to qualify as persons? If we can answer this question then we can identify persons and this answers all sorts of questions about how we should treat all kinds of beings. Work on your own to write a short paragraph on which is the criterion of personhood and why. Try to explain why this characteristic is significant. Remember we are looking for a characteristic in virtue of which the being has moral status. Here are some answers philosophers have given. Which one is the most convincing? These five abstracts correspond to the five criteria mentioned above, i.e. rationality, membership of a moral community, membership of the human species, having interests and sentience.

Immanuel Kant

“Now I say that man, and in general every rational being, exists as an end in himself, not merely as a means for arbitrary use by this or that will: he must in all his actions, whether they are directed to himself or to other rational beings, always be viewed at the same time as an end…Beings whose existence depends, not on our will, but on nature, have none the less, if they are non-rational beings, only a relative value and are consequently called things. Rational beings, on the other hand, are called persons because their nature already marks them out as ends in themselves – that is, as something which ought not to be used merely as a means – and consequently impose to that extent a limit on all arbitrary treatment of them…Persons, therefore, are not merely subjective ends whose existence as an object of our actions has a value for us; they are objective ends – that is, things whose existence is in itself an end, and indeed an end such that in its place we can put no other end to which they should serve simply as a means…” (Kant I. [1785] . The Groundwork of the Metaphysic of Morals, in Paton H.J., The Moral Law (London: Routledge, 1948), 428).

Noddings Nell

“Ethical caring, the relation in which we do meet the other morally, will be described as arising out of natural caring – that relation in which we respond as one-caring out of love or natural inclination. The relation of natural caring will be identified as the human condition that we, consciously or unconsciously, perceive as ‘good’. It is that caring toward which we long and strive, and it is our longing for caring – to be in that special relation – that provides the motivation for us to be moral…We behave ethically toward one another…because we carry with us the memories of and longing for caring and being cared-for. There is a transfer of feeling and an opportunity – an invitation of sorts – to commit ourselves to the recognition of this feeling and to the continuing receptivity that will bring it to us again and again. But…our obligation to summon the caring attitude is limited by the possibility of reciprocity. We are not obliged to act as one-caring if there is no possibility of completion in the other.” (Noddings N, Caring: a Feminine Approach to Ethics and Moral Education, (Berkeley: University of California Press, 1984) abstracts from pp.4-5 and 149)

John Noonan

“Once conceived, the being (the human foetus) was recognized as man because he had man’s potential. The criterion for humanity, thus, was simple and all-embracing: if you are conceived by human parents, you are human…The positive argument for conception as the decisive moment of humanization is that at conception the new being receives the genetic code. It is this genetic information which determines his characteristics, which is the biological carrier of the possibility of human wisdom, which makes him a self-evolving being. A being with a human genetic code is man.” (Noonan J.T., “Abortion is Morally Wrong” in Pojman L., Life and Death: grappling with the moral dilemmas of our time (California: Wadsworth, 2000), pp.269-70 and 273. Peter Singer “The essence of the principle of equal consideration of interests is that we give equal weight in our moral deliberations to the like interests of all those affected by our actions…What the principle really amounts to is: an interest is an interest, whoever’s interest it may be…The argument for extending the principle of equality beyond our own species is simple, so simple that is amounts to no more than a clear understanding of the nature of the principle of equal consideration of interests…[T]his principle implies that our concern for others ought not to depend on what they are like, or what abilities they possess (although precisely what this concern requires us to do may vary according to the characteristics of those affected by what we do). It is on this basis that we are able to say that the fact that some people are not members of our race does not entitle us to exploit them, and similarly the fact that some people are less intelligent than others does not mean that they interests may be disregarded. But the principle also implies that the fact that beings are not members of our species does not entitle us to exploit them, and similarly the fact that other animals are less intelligent than we are does not mean that their interests may be disregarded…The capacity for suffering – or more strictly, for suffering and/or enjoyment or happiness – is not just another characteristic like the capacity for language, or for higher mathematics…The capacity for suffering and enjoying things is a prerequisite for having interests at all, a condition that must be satisfied before we can speak of interests in any meaningful way…If a being suffers, there can be no moral justification for refusing to take that suffering into consideration. No matter what the nature of the being, the principle of equality requires that its suffering be counted equally with the suffering – in so far as rough comparisons can be made – of any other being.” (Singer P., Practical Ethics (Cambridge: Cambridge University Press, 1979), pp.19, 49-50

Michael Tooley

“An organism possesses a serious right to life only if it possesses the concept of a self as a continuing subject of experiences and other mental states, and believes that it is itself such a continuing entity…To ascribe a right to an individual is to assert something about the prima facie [“on the face of it”, i.e. binding but defeasible] obligations of other individuals to act, or to refrain from acting, in certain ways. However, the obligations in question are conditional ones, being dependent upon the existence of certain desires of the individual to whom the right is ascribed…[T]he expression ‘right to life’ is misleading, since what one is really concerned about is not just the continued existence of  a biological organism, but the right of a subject of experiences and other mental states to continue to exist…The final stage of the argument is simply a matter of asking what must be the case if something is to be capable of having a desire to continue existing as a subject of experiences and other mental states. The basic point here is that the desires a thing can have are limited by the concepts it possesses…[A]n entity cannot be the sort of thing that can desire that a subject of experiences and other mental states exist unless it possesses the concept of such a subject. Moreover, an entity cannot desire that it itself cotinue existing as a subject of experiences and other mental states unless it believes that it is now such a subject” (Tooley M., “Abortion and Infanticide” in Kuhse H. and Singer P. (ed), Bioethics: an anthology (Oxford: Blackwell, 1999) pp.24-5.


In discussing these positions with your students look out for these common mistakes:

-         Understanding what we mean by ‘rationality’ is quite a difficult topic. In the way these writers use it, it tends to be a distinguishing feature of human beings, i.e. what separates us from animals is reason. This means that rationality is not something we have more or less of, unlike intelligence in the IQ sense of the word, but a capacity which characterizes our species.

-         When discussing rationality as the characteristic of persons it is not clear whether severely mentally disabled humans might qualify as persons since they are members of the species whose distinguishing characteristic is rationality, or might not qualify as they do not meet the minimum cognitive criteria for rational thought. Kant did not comment on this issue as such and it is left up to modern commentators to decide how to interpret his theory.

-         Warn your students that some writers in the literature use ‘person’ and ‘human’ interchangeably. We have defined these terms differently to help explain the debate. For us ‘person’ is a technical term which refers to beings of moral worth, the question is still open whether any beings (including humans) qualify for personhood. The term ‘human’ is reserved for members of the human species, defined in biological terms and as distinct from other species such as canine or feline. Sometimes the term ‘humanity’ is use. This is an ambiguous term. If understood in a biological sense, it should be clear which beings share our humanity, i.e. only human beings. However, it is often used equivocally to mean what is morally special about human beings. Notice that now we have presupposed that human beings are persons due to their humanity and we are asking whether other beings, e.g. higher primates, share in this humanity. Using this term in this way tends to muddle up the discussion completely!

-         Often I have students equate the term ‘foetus’ with ‘human’ which in turn they assume to mean ‘person’. This contains two fallacies. The first is that the term ‘foetus’ refers to a specific developmental period of mammals and as such we can have feline fetuses, canine fetuses and human fetuses (if your students are confused about this ask them: “Suppose my cat is pregnant. What do you call the beings in her womb?”, the odd person may say ‘kittens’, but take this opportunity to highlight the importance of understanding concepts!). The second fallacy is to assume that ‘human’ by default means ‘person’. The discussion in this session should make it clear why this is wrong.

-         The equal consideration of interests principle may require a bit more elucidation. Singer remarks that some beings have interests and some objects do not. What distinguished the two is having the capacity for pain and pleasure (which is the most basic kind of interest a being can have). We should respect cats, for example, because they, unlike chairs, feel pain. What this respect means is respect for their interests, we have a compelling moral reason to promote pleasure and prevent pain. Another important point in this theory is that everybody’s interests count the same. Suppose we could measure pain, then one unit of my pain is as bad a thing as one unit of yours and one unit of a cat’s pain. This does not mean that my pain at my amputated and untreated leg is the same as your minor headache of course! Nor does it mean that some beings, such as humans, have a vivid emotional life and therefore have a greater number of complex interests than simpler organisms. What it does mean is that each interest should count equally and decisions should be made by taking equal consideration of every being’s interests. 

-         Some of Singer’s claims have provoked great controversy, for example he is often accused of arguing that we are better off carrying out medical research on mentally disabled humans than on animals. What he does say is that if we give equal consideration to everyone’s interests, then a very severely mentally disabled human may have less to lose by being experimented on than a higher primate. This needn’t imply that we should experiment on disabled humans, but it does imply that we should not experiment on primates first.

-         Tooley’s sentience criterion may be quite difficult to use in order to distinguish between different beings. Again the adult human case is the easy one, but how we should understand sentience can be problematic (awareness, self-awareness, emotions, etc.) and even worse it is not clear how we should go about measuring whether different beings are sentient. Is a gorilla or a pet dog, or a goldfish or a snake or a snail sentient? How do we measure this? Some experiments rely on recognizing oneself in a mirror, or the ability to lie, or the ability to recognize kin and maintain ties to other beings, or refusing to eat the flesh of members of your species, however just a cursory look at the variety of these experiments should illustrate how difficult this question is.


Descrates on knowledge

This is my favorite exercise as it is the first one I ever used. It was suggested to me by Eve Garrard who was kind enough to respond to a request for help with teaching ideas (a request from a graduate student she had never met before who was studying in another University!).


My students had been to a lecture on Cartesian doubt, but were slightly lost. Partly this was because the question did not make sense to them, what do you mean what do I know, knowledge is self-explanatory! And partly because the answer was a bit odd, especially the stuff about demons! In the seminar rather than going over the same material as the lecture, Eve suggested a radical approach: walk in and ask everyone to write down something they know – any proposition of the form “I know that X” would do. Now ask everyone to pair up and challenge the other person’s claim to knowledge. Pretend your life depends on finding grounds to challenge this bit of knowledge your pair is laying claim to. You can leave the students to do this for a few minutes and then bring everyone together. Put all the knowledge claims on the board and ask the students to relate back their challenges. Almost inevitably you will come across people who use a regress, claims about omniscient persons (usually someone’s mum), etc. If you are lucky you might get an a priori truth (someone must have been paying attention at the lecture!), set this one aside for the time being. Hopefully your students will challenge all the knowledge claims (somehow this is easier to do if it is someone else’s claim rather than your own – I suppose it might be because other people never know what they are talking about!) and you can give a bit of structure to the discussion by then relating their challenges to the three Cartesian arguments. Finally return to the a priori truth, see if the students understand why this cannot be challenged, if they get this give them the Cogito and send them off to think about challenging it for a week before the next seminar.