A theory of human nature is an account of what sort of things humans essentially or really are, or are like. Such an account may lead to consequences in many philosophical areas: for example in political philosophy it may be argued that humans are naturally acquisitive and selfish and that these characteristics lead inevitably to institutions such as private property and the desire for status; on the other hand it may be argued that these features are not part of the natural human make-up but come about as the result of humans living in unnatural kinds of societies. Similarly, a view of human nature may influence our accounts of issues as diverse as how we make moral or aesthetic judgements, our claims to knowledge about the external world, or whether there is the possibility of human survival after death.
This article will examine two accounts of human nature, those found in Descartes and Hume. It will not attempt to assess the plausibility of either account – this will be left to the reader – but will be an exploration of what form a theory of human nature may take, and what such a theory is attempting to account for.
From the beginning of the Discourse on the Method, Descartes makes claims about the nature of humans. For example, in only the second paragraph he writes:
…as regards reason or sense, inasmuch as it is the only thing that makes us men and distinguishes us from brutes, I should like to hold that it is to be found complete in each of us… (Descartes, 1637, p. 7)
Here Descartes is making two claims about reason: firstly it is a uniquely human characteristic, not shared by other animals; secondly is a characteristic that all humans share. These claims are connected and as I will be giving more attention to the first claim, I will only briefly discuss the second. When, in the second part of the Discourse, Descartes proposes to rid himself of his previous beliefs in his search for knowledge, he gives as a justification the differences that exist between, as he says, “the best qualified” that he has come to see as a result of his education and travels. As he puts it, quoting Cicero, “one can imagine nothing so strange and incredible but has been said by some philosopher” (Descartes 1637 p.18). However, these views are deserving of respect as
…those whose opinions are quite opposed to ours are not, for all that, without exception barbarians and savages; many of them enjoy as good a share of reason as we do, or better. (Descartes, 1637, p.19).
So reason is a universal characteristic. We should look not so much at what opinions other peoples have arrived at but how they arrived at them, and we may even find that their ability to reason was better than ours. But what of the ‘barbarians and savages’? They are clearly human – by species – but seem to be excluded by Descartes. To understand this we must look at what distinguishes us from other animals.
Before discussing animals it is worth looking at what Descartes says about machines. His view is that if there were machines that looked like animals, down to their internal details, we would have no way of distinguishing them from animals; on the other hand any such machine that resembled a human would be distinguishable for two reasons. Firstly they could never use language in the way that we do (Descartes, 1637, p. 41). To be sure, they could be made to produce words in response to their surroundings and physical stimuli. However, such a machine would not match human sophistication as it could not be that
… it should be so made as to arrange words variously in response to the meaning of what is said in its presence, as even the dullest men can (Descartes, 1637, p.42) .
Secondly, such machines would be specialised to a particular task:
…while they might do many things as well as any of us or better, they would inevitably fail in others, revealing, that they acted not from knowledge but only from the disposition of their organs (ibid.).
Because of this they lack reason, as reason is a “universal tool” that serves in all circumstances.
Exactly the same two points can be applied to distinguish humans from other animals, claims Descartes. Firstly, animals cannot use language and all humans can do this:
…there are no men so dull and stupid, not even lunatics, that they cannot arrange various words and form a sentence to make their thoughts understood; but no other animal … can do the like. (ibid.).
This is intended to show that animals have a complete lack of reason and not merely a lesser degree of it. Even the best monkeys or parrots are not comparable in this respect to “one of the stupidest children or at least a child with a diseased brain” which shows that their “souls” are “wholly different in nature from ours”.
Secondly, animals display the same limitations as machines:
…although several brutes exhibit more skill than we in some of their actions, they show none at all in many other circumstances; so their excelling us is no proof that they have a mind, for in that case they would have a better one than any of us and would excel us all round; it rather shows that they have none… (Ibid.)
So the ability to reason is what separates us from other animals. In fact, for Descartes the error of believing that animals have reason and consequently minds, is second only to the error of denying the existence of God as being likely to turn “weak characters from the strait way of virtue”.
In showing how much we differ from other animals, Descartes also gives a further indication of what characteristics all humans share. As was remarked earlier, Descartes seemed to exclude “barbarians and savages'” from those who could reason. However, Descartes says that animals do not have the abilities of “the dull and stupid”, “lunatics”, “the stupidest children” and even a child with a “diseased brain”. It would seem then that the “barbarians and savages”, despite their lack of culture, would be allowed to share in reason.
So, for Descartes, reason is a vital characteristic. The ability to reason is the feature of a mind, which is a different substance from matter, and is the thing that allows our immortality. The ability to reason is, then, an essential human characteristic, not shared by other animals. This claim is, however, disputed by Hume.
Hume displaces reason from the position that those such as Descartes would give it. Throughout A Treatise of Human Nature, Hume shows again and again that reason is insufficient: for example, reason does not provide us with an explanation of cause and effect; nor with an argument for the existence of the external world; nor an account of personal identity. Reason is found in varying degrees in different people: in a long note in the Enquiry Concerning Human Understanding Hume lists some of these, such as differences in memory, attention and observation, the ability to carry out long chains of argument without confusion, biases of prejudice and education, and so on (Hume, 1748, p. 107). Reason is found in animals to be much the same as it is in humans:
… and no truth appears to me to be more evident, than that beasts are endow’d with thought and reason as well as man. (Hume, 1739, p. 226).
When a dog avoids fire and strangers, but “caresses his master”, for example, the dog relies on its senses and memory and draws inferences from experience in the same way that we do (op cit. p. 227). So if reason is not central to human nature, what is?
To understand Hume’s views it is important to see what he means by the “attempt to introduce the experimental method of reasoning into moral subjects” that is in the title of the Treatise. Hume intends to give a naturalistic account of humans, that is to treat the study of humans in the same way that the natural sciences treat their subjects. An example of this sort of procedure is supplied by Hume’s treatment of free will and determinism. Hume is a determinist in as much as he believes human behaviour to be predictable, and this predictability is of the same kind as the predictability of any natural phenomena. If a traveller reported that in a country of the same northern latitude as ours the fruit ripened in the winter and decayed in the summer, that is in the opposite way to which it occurs in this country, they would be believed as much as if they had reported people of the same character as those in Plato’s Republic or Hobbes’ Leviathan (Hume, 1739, p. 450). A prisoner discovers the impossibility of escape as much from the obstinacy of the jailer as from the stones and bars of the cell, and foresees death as much from the “constancy and fidelity” of the guards as from foreseeing their head being cut off from their body (op. cit. p. 454). So in the same way that we learn any facts about the world – from observation – we will have to learn the facts about human nature in the same way.
When discussing ethics, Hume concludes that there are no moral truths to be observed in the world and that reason cannot supply a basis for ethics either. Morality is a matter of feeling, or as Hume would say, sentiment. In looking for the wrongness of an action
The vice entirely escapes you, as long as you consider the object. You never can find it, till you turn your reflection into your own breast, and find a sentiment of disapprobation, which arises in you, towards the object (Hume, 1740, p. 520) .
But if morality is simply a matter of feeling, and reason plays no role other than informing us of the existence of the objects of our desires and the best means to attain them, then why don’t we just do anything that we feel like? Hume is famously quoted as saying
‘Tis not contrary to reason to prefer the destruction of the whole world to the scratching of my finger (Hume, 1739, p. 463) .
However, Hume is seldom quoted from the immediately following passage:
‘Tis not contrary to reason for me to chuse my total ruin, to prevent the least uneasiness of an Indian or person wholly unknown to me (ibid.).
If reason is “the slave of the passions” then why should we do one thing rather than another, and why should one course of action be right – that is produce a sentiment of approval – and another wrong? We have, Hume acknowledges, a certain self-love but we also share an amount of sympathy with other humans. While it is “rare to meet with one, who loves any single person better than himself” it is equally “rare to meet with one, in whom all the kinds of affections, taken together, do not over-balance all the selfish” (Hume, 1740, p. 538). Moral views are formed, in large part, by this feeling of sympathy.
There are in all sciences certain general principles that cannot be examined further, and that there are similarly certain facts concerning human nature about which we can enquire no further is evident to Hume. Such a fact is that ‘No man is absolutely indifferent to the happiness and misery of others (Hume, 1751, p. 178-9 n.). We naturally feel more for those closer to us by family, country or time than those more distant, but we do feel sympathy, to some extent, for everyone:
Would any man, who is walking along, tread as willingly on another’s gouty toes, whom he has no quarrel with, as on the hard flint and pavement (Hume, 1751, p. 226)?
How much sympathy we feel for others may be open to debate (ibid.) but that we do feel some sympathy has to be admitted. Hence, for Hume, sympathy is a feature shared by all humans, and that feature which provides a basis for ethics.
To end this article, I would like to make some observations about the preceding discussions of Descartes and Hume. Firstly, any one of three things may be meant by a “theory of human nature”: some characteristic that is shared by all humans; or some characteristic that is distinctly human and makes us different from other animals; or some human characteristic that can provide a grounding for morals. As we have seen, Descartes proposes that reason is a shared human characteristic which makes us different from other animals, while Hume rejects this and claims that sympathy is a shared human characteristic and that this provides a basis for morals.
My second point is that any one of the above three theses may be taken to be a view of human nature and that both Descartes and Hume in fact propose views that commit them to two of them. Now my discussion so far has attempted to be descriptive of Descartes and Hume but it may be possible to extend their positions. As we have seen, Descartes proposes that reason is a characteristic shared by all humans and not by other animals. Reason could, then, be seen to be a special characteristic that distinguishes humans from animals, and indeed from all other things in the world, and so commit us to treating humans in a different way from other things in the world; as all humans share this feature, all humans should be treated in this way. That is, the view that all humans share this feature, and no other thing has this feature, may provide a grounding to morals. Hume, on the other hand, proposes that sympathy is common to all humans and is a basis for morals. Now it may be that sympathy is not a feature found in other animals (would another animal tread willingly on someone’s gouty toes?) and so other animals should not be subject to moral appraisal, nor able to formulate moral principles themselves. In short, I am suggesting that our commitment to any one of the above theses concerning human nature may commit us to views on the other two.