The translation of this new edition of Immanuel Kant’s Groundwork of theMetaphysics of Morals first appeared in my German–English edition(Cambridge, 2011). It is based on Mary Gregor’s English version, firstpublished by Cambridge University Press in 1996 and subsequentlyreprinted in the Cambridge Texts in the History of Philosophy.

Throughout the revision process, care was taken to preserve thefamiliar feel of Gregor’s work. While there were many changes in mattersof detail, explained in the introduction and notes to the bilingual edition,the principles of her approach – combining a high degree of faithfulnessto Kant’s German with readability and fluency – naturally remainedintact.

The Groundwork was first published in 1785. The translation followsthe German text of the German–English volume, which is based on thesecond original edition of 1786. All major departures of the secondoriginal edition from the first are documented in the footnotes of thisvolume.

The concept of freedom is the key to the explanation of the autonomy of the will

A will is a kind of causality of living beings in so far as they are rational, and freedom would be that property of such a causality, as it can be efficient independently of alien causes determining it; just as natural necessity is the property of the causality of all non-rational beings to be determined to activity by the influence of alien causes.

The explication of freedom stated above is negative and therefore unfruitful for gaining insight into its essence; but there flows from it a positive concept of freedom, which is so much the richer and more fruitful. Since the concept of causality carries with it that of laws according to which, by something that we call a cause, something else, namely the consequence, must be posited: freedom, though it is not a property of the will according to natural laws, is not lawless because of that at all, but must rather be a causality according to immutable laws, but of a special kind; for otherwise a free will would be an absurdity. Natural necessity was a heteronomy of efficient causes; for every effect was possible only according to the law that something else determines the efficient cause to causality; what else, then, can 4:447 freedom of the will be, but autonomy, i.e. the property of the will of being a law to itself? But the proposition: the will is in all actions a law to itself, designates only the principle of acting on no maxim other than that which can also have itself as its object as a universal law. But this is just the formula of the categorical imperative and the principle of morality: thus a free will and a will under moral laws are one and the same.

It is impossible to think of anything at all in the world, or indeed even beyond it, that could be taken to be good without limitation, except a good will. Understanding, wit, judgment, and whatever else the talents of the mind may be called, or confidence, resolve, and persistency of intent, as qualities of temperament, are no doubt in many respects good and desirable; but they can also be extremely evil and harmful if the will that is to make use of these gifts of nature, and whose distinctive constitution is therefore called character, is not good. It is just the same with gifts of fortune. Power, riches, honor, even health, and the entire well-being and contentment with one’s condition, under the name of happiness, inspire confidence and thereby quite often overconfidence as well, unless a good will is present to correct and make generally purposive their influence on the mind, and with it also the whole principle for acting; not to mention that a rational impartial spectator can nevermore take any delight in the sight of the uninterrupted prosperity of a being adorned with no feature of a pure and good will, and that a good will thus appears to constitute the indispensable condition even of the worthiness to be happy.

Some qualities are even conducive to this good will itself and can make its work much easier; but regardless of this they have no 4:394 inner unconditional worth, but always presuppose a good will, which limits the high esteem in which they are otherwise rightly held, and makes it impermissible to take them for good per se. Moderation in affects and passions, self-control and sober deliberation are not only good in many respects, they even appear to constitute part of the inner worth of a person; but they are far from deserving to be declared good without limitation (however unconditionally they were praised by the ancients). For without principles of a good will they can become most evil, and the cold blood of a scoundrel makes him not only far more dangerous, but also immediately more loathsome in our eyes than he would have been taken to be without it.

The individual in the crowd

In this final chapter, we draw together the threads of evolution, causation, development and phylogeny that have run through this book and show how they underlie one of the most striking features of animal lives – their tendency to be social. Tinbergen's four questions have stood the test of time, they are as important as they ever were and as he did in his pioneering book, The Study of Instinct (1951), we shall attempt a synthesis involving them all. Our knowledge of animal behaviour has grown enormously since Tinbergen's time and has spawned whole new disciplines such as behavioural ecology and neuroethology, but there is still much be gained by asking his different kinds of questions about behaviour. Asking how (causally) animals choose their mates, for example, is hugely illuminated by understanding why (in an evolutionary sense) they choose the mates they do, and vice versa. Since virtually all animals are social for at least part of their lives, social behaviour provides an obvious base for a synthesis of many aspects of behaviour across a wide range of species.

When we observe flocks of birds, swarms of insects or herds of antelope, it is easy to lose sight of the individual in the crowd. If a group stays together, it is because individual animals all benefit from staying with one another.

It is 14 years since the last edition and the science or sciences of animal behaviour have progressed enormously. Topics which justified only a brief mention in an introductory text then, for example sperm competition as a factor in mating systems, have prospered to require textbooks of their own. How then to approach a new edition which cannot be allowed to become significantly larger.

It is our conviction that an introduction to the whole field, or at least a substantial part of it, remains as important as ever. Discussing new areas of research is best done from a firm basis of the basic concepts and for us these are still embodied in Niko Tinbergen's 1963 ‘Four Questions for Ethology’ – function, evolution, causation and development. So the plan of our book remains essentially that of the other editions. There has been some extensive rewriting and we have tried to give good coverage to those areas where there have been important advances, notably in the evolution of behaviour and its development. We continue to give extensive references so that readers can easily get into the literature of areas that catch their interest. There is a great deal of new literature to be explored but we have never cited new work unless it really adds something. Often concepts are best illustrated by some of the now classical papers.

Evolution by natural selection is the great unifying concept of biology, so much so that most biologists now feel that, without it, none of the phenomena they study really make sense. Richard Dawkins (1986) provides an excellent modern survey of the great explanatory power of what has come to be called ‘neo-Darwinism’. Natural selection, operating on random, inherited variation has, over the generations, shaped animals to match the environments in which they live. Sometimes adaptation has been achieved through genes, accumulated over many generations, biasing the development of behaviour directly into appropriate responses. In other cases, animals inherit only biases to respond adaptively to their immediate environment so as to acquire, individually, appropriate responses by learning. Much behaviour develops by a mingling of such processes. All through this book we have emphasized the adaptive role of behaviour in an animal's life and so the concepts of ‘evolution’ and ‘adaptation’ have been implicit in much of what has already been said. Now we look at them in more detail.

In fact, not just one but two of Tinbergen's four questions are about the evolution of behaviour. One of them, about ‘adaptiveness’, is about how behaviour that we see present-day animals doing helps them to survive and reproduce. The other, about phylogeny, is about the changes in behaviour that have taken place over evolutionary time.

Just before dawn, a red junglefowl (Gallus gallus) cock crows from his roost in the bushes. Then, as it begins to get light, he makes his way to the ground with his group of three females and starts his daily search for food, scratching in the leaf litter for seeds and, if he is lucky, worms and grubs. In the heat of the day, he will return to the bushes for a siesta, but later he will resume his feeding on the ground, perhaps breaking off to dustbathe, mate with the females or search for water. All the time, he keeps a wary eye out for predators and rival males, ready to disappear into the undergrowth or see off an intruder at a moments' notice. As it gets dark, the group leave the ground in preparation for spending the next night in the relative safety of the bushes.

This simple description of the day in the life of one animal illustrates perfectly just how complex animal behaviour is. At every moment of every day an animal can be said to be making ‘decisions’ about what to do next – choosing to do one thing rather than another, or choosing to stop what it is doing and start something else. And those decisions can be studied at every level ??? from the level of the whole day, in which the decisions are between which parts of the day to be active and which parts to hide or sleep, right down to the moment-to-moment decisions about whether at this second to peck down at a food item or look up to see if there is a predator around. Indeed, we can look at even longer time scales, such as how behaviour changes over a whole year or even a whole lifetime.

Behaviour can be so well adapted to an animal's way of life that the animal seems to ‘know’ what to respond to, what to do and when to do it. Thus partridges and small rodents ‘know’ that the most effective defence against a hawk flying overhead is to flatten themselves on the ground and remain motionless since the hawk, which is very sensitive to movement, is least likely to see them. Most of us have experience of wasps that know about sweet drinks or mosquitoes that know where to find exposed human flesh.

Using the word ‘know’ in this context does not necessarily imply that animals are consciously thinking about what they are doing (although they may be, as we discuss in Chapter 5). Animals may ‘know’ things about their environments in the same way that a heat-seeking missile knows how to find its target or a computer knows how many mistakes you have made in the course of a game. In other words, quite simple unconscious mechanisms are capable of giving rise to what we might refer to as knowledge. When we ask causal questions about behaviour, we are asking what this knowledge is and how the animal uses it.

Learning as part of adaptation

Throughout this book we have made frequent reference to learning as a form of behavioural development retained into adult life and as one pathway by which behaviour becomes adapted to an animal's requirements. Now attention must be focused on learning itself. Learning and memory go together because whilst the former involves changing behaviour as a result of experience, its effects cannot be put to use unless the results of the experience can be stored in some way and recalled the next time they are needed. A discussion of learning will finally lead us on to a consideration of the mental or cognitive abilities of animals and how far they share some of those abilities with ourselves. The issues raised there take us far beyond just learning abilities but it is essential first to consider what are the different types of learning and biologists will want to examine how and whether they are expressed in a range of very different animals. For this reason, Thorpe's (1963) book, although old, remains useful because it does deal with the whole animal kingdom. It covers something of the context and the phenomena associated with learning in molluscs and insects, fish and amphibians, as well as the more familiar studies with birds and mammals.

One of the most remarkable features of living organisms – plant or animal – is the way in which a single-celled zygote, the fertilized egg, is transformed by cell division, cell differentiation and cell movement into the adult form, far more complex and often millions of times larger. Development (often called embryology when it describes the progress from egg to a young but free-living stage) is a most challenging field of research and there has been some remarkable progress in recent years. New insights help us to understand how the sequences of development have been modified as a group of animals has evolved, for example as the vertebrates have evolved through fishes, amphibians and reptiles to birds or mammals. The initial stages must stay the same and modifications can be added only at the end. Thus all vertebrate embryos go through a stage which involves their developing gill clefts. Fish – of course – retain these and so do some amphibians but in reptiles, birds and mammals they close up as other structures pertaining to their future life on land are added on and replace them. Hence the old phrase, ‘ontogeny recapitulates phylogeny’ which retains its power if not taken too literally.

Young animals grow up

The zygote contains all the information necessary to build a new organism, provided that it can develop in and interact with a suitable environment. When we study the development of behaviour, we must obviously concern ourselves with some aspects of embryology – for example, the way in which the basic framework of the nervous system is laid down – but we need to go far beyond this.