On the basis of (a) common sense, (b) findings in cognitive ethology (the study of animal thinking, consciousness and mind) and (c) the notion of evolutionary continuity, a strong case can be made for admitting great apes into the community of equals. Initially, I was incredulous that such an appeal was even necessary. Next, I found it difficult to conceive that this plea could ever be denied, not only to great apes, but to most nonhuman animals. Considering, however, how many nonhumans are used by humans for anthropocentric ends, I came to see that it was my own stance that was unusual and in need of justification.

Thinking about great apes as members of the community of equals has also made me think about some aspects of what it is like to be a scientist. My early training was an instance of what Bernard Rollin calls 'the common sense of science',[1] in which science is viewed as a fact-gathering value-free activity. There was little or no overt expression of concern for the plight of nonhumans, and questions concerning morals and ethics rarely arose. When such questions did surface, they were invariably dismissed by invoking a vulgar form of utilitarianism, in which suspected costs and benefits of animal use were assessed from the human's point of view with little or no concern for the nonhuman's perspective. Often, it was simply asserted that the animals really didn't know or care what was going on. This apathy and remoteness from the animals' points of view bothered me deeply. I soon formed the opinion that ethical issues are integral and legitimate parts of science; one cannot be neutral on such matters. 'Moral privatists' who dispense with their moral and ethical obligations to nonhumans are taking a position on matters even though they are not aware of doing so.[2]

My own laboratory and field experience in ethology showed me that all behavioural research involves intervention, even 'simple observation'. I asked myself just what humans do when they study nonhumans and questioned what science was all about. I engaged in these thoughts not because I wanted to terminate my career or others' research, but because I thought it reasonable to think about behavioural biology specifically, about science in general, and also about how I spent a lot of my time. Among my scientific colleagues, my contemplation of animal welfare and questioning of science is not always well received. Recent accusations by some prominent scientists concerning the presumed intentions and characteristics of those who are interested in animal rights and animal welfare have made it essential to stress that I am not (and have never been) anti-science[3] or an anti-intellectual or Luddite.[4] Furthermore, I certainly do not want to end all research relating to animals.[5] For example, if some primates must be kept in protected areas because they were bred in captivity and it would not be in their interests to return them to the wild, or the habitat from which they came has disappeared, research that could lead to improvements in their welfare, and caused them no harm, would be permissible. Some research on animals who had already been injured, either physically or psychologically, might also be acceptable if the animals were not to suffer any further harm. In general, as far as apes are concerned, some studies would be permissible on the same basis as they would be permissible on humans incapable of giving consent: that is, where a guardian appointed to represent the best interests of the apes would give consent. While I value science, I do not worship the enterprise of science, and one does not have to be anti-science or anti-intellectual to question how science is done.[6]

Great Apes and the Community of Equals

There seem to be at least three interrelated reasons why great apes should be included in the community of equals. The first concerns the use of common sense to describe and to explain animal behaviour, the second is motivated by recent work in comparative and evolutionary cognitive ethology and the third centres on the notion of evolutionary continuity, stemming mainly from the work of Charles Darwin.

Common-sense approaches to the study of animal behaviour are useful in furthering our understanding of the behaviour of animals. The ways in which humans describe and explain the behaviour of non-humans can strongly colour views on animal welfare. Without the use of common sense and familiar anthropomorphic terms, descriptions and explanations of animal behaviour are tedious and inconvenient; they frequently lack context and content, and do not tell us very much (if anything) about what might have occurred in a given situation. Even if explanations of animal behaviour based on common sense or folk psychology are sometimes wrong (as are 'scientifically' based explanations), they can also be correct.

Data from comparative evolutionary studies in cognitive ethology — investigations into animal thinking, awareness and consciousness - also support the suggestion that great apes should be admitted to the community of equals. It has become clear that many nonhumans have rich cognitive and intentional lives[7] and also have the capacity to experience pain and to suffer; studies in cognitive ethology inform questions concerning animal cognition and animal welfare, especially when the level of development of an individual's (or species') cognitive abilities are used as a basis for moral and ethical decisions. The richness of the cognitive and intentional lives of great apes is particularly evident, as many of the essays in this book make clear.

There is also an evolutionary reason for claiming that great apes deserve membership in the community of equals. Evolutionary continuity is widely accepted by biologists, even when it is not very apparent. Ethological studies of nonhuman primates in general, and great apes in particular — species with which humans are most closely evolutionarily continuous — can certainly inform and motivate investigations into human behaviour.[8] We readily acknowledge evolutionary continuity in physiology and anatomy, and we should do so in behaviour. Some common sense is important here: can we really believe that humans are the only individuals with feelings, beliefs, desires, goals, expectations and the ability to think about things?

Those who deny that animals have beliefs or desires or propositional attitudes of different orders must offer alternatives that will be as useful for describing and explaining animal behaviour, and this they have not done. How can one deny that a great ape has some beliefs about what h or she is doing, even if the ape's beliefs are not like ours? While I do not really know that an ape expects (or has a belief) that food will be forthcoming when he or she engages in a behaviour that most humans call 'begging', I feel that this word adequately describes what he or she is doing. Likewise, when Jethro chases another ape up what I call a ‘tree’ it does not really matter whether Jethro knows that it is an 'ape' who ran up a 'tree'; Jethro does not need to have the concepts of 'ape' and ‘tree’ to engage in what we call 'ape-chasing'. I use English, the language with which I am most familiar, to convey information about Jethro to others who also understand English. I also use anthropomorphic words and phrases that seem most likely to capture the essence of what he is doing. I could describe, in great and inconvenient detail, Jethro's behaviour from anatomical and physiological perspectives, but this approach would convey little or no useful information to another person about what Jethro was doing.

Of course, it is very difficult for one to know with certainty what is going on in the minds of other individuals, human or nonhuman. Some sceptics conflate the difficulty of learning about animals' cognitive lives with the impossibility of doing so. Stephen Stich claims that because we cannot say what it is that an animal believes - because we cannot precisely ascribe content- it is fruitless to suggest that we can explain an animal's behaviour in terms of desires and beliefs.[9] More plausibly, Donald Davidson, although he is sceptical about animals having beliefs, notes that we have no general and practical alternative for explaining animal behaviour other than by attributing beliefs, desires and intentions.[10] He also holds that although language is not necessary for thought, it is difficult to imagine that there would be much thought without language.[11] None the less, Davidson does not believe that the possible absence of thought or of propositional attitudes in nonhumans means that nonhumans may be mistreated. Furthermore, demanding that nonhumans have language (as we know it) before they can ha propositional attitudes, and requiring that animals have propositional altitudes before they can be granted rights or their interests receive equal consideration to those of humans, is anthropocentrically self-serving and asserts an extremely narrow view of what it is like to be nonhuman animal.

Investigation into the cognitive skills of nonhumans frequently h surprising results, and it is essential that people who write about animal issues be cognisant of these findings. It is difficult to imagine how any coherent thoughts about moral and ethical aspects of the treatment animals could be put forth without ethological, evolutionary a philosophical input. Clearly, ethologists must read philosophy and philosophers must not only read ethology but also watch animals.

Conclusion: The Importance of Ethological Research

Humans need to make serious attempts to look at things from a nonhuman point of view and to try to discover answers to the fascinating question of how animals interact in their own worlds and why they do so. There is no substitute for careful ethological research. While some animals seem to respond in the same way as humans to a wide variety of stimuli that are known to us to be pleasurable or painful, and arguments from analogy are often very convincing, we also know that many other animals process sensory information differently from humans and that they perform motor activities that are unlike any that humans typically perform. In these cases, arguments from analogy may fail, but this does not mean that they always fail. Furthermore, we should not conclude that any animals, human or nonhuman, cannot do something when they do not do what we expect them to do. We must be sure that the animal can perceive the necessary stimuli, is able to perform the motor activity that we think he or she should perform, and is motivated to perform this task. Furthermore, when an animal makes what we call an 'error', it may not be an error in the context in which it was made - when the animal's sensory and motor worlds are taken into account.

Adopting a common-sense approach to how we view the cognitive skills of nonhumans and their pains and suffering will make this a better world in which humans and nonhumans can live compatibly. Common-sense intuitions about pain, suffering and animal cognition should be combined with reliable empirical data, of which there are already plenty. Some claim that cognitive explanations have yet to prove their worth when compared with reductionist behaviouristic explanations of the behaviour of nonhumans.[12] Such sceptics ignore a wealth of data that demonstrate rather impressive cognitive skills in many nonhuman animals; they may also mislead those who look to cognitive ethology to provide information for structuring their ideas about animal welfare, and conclude that there is little or nothing in cognitive ethology that is convincing. What we believe about the cognitive capacities of nonhumans affects our thinking about animal welfare; different views lead us to look at animals in particular ways. Ascribing intentionality and other cognitive abilities to animals is not moot, because it has moral consequences. Common sense, findings in cognitive ethology and the idea of evolutionary continuity strongly support the present appeal for admitting great apes into the community of equals. In the future, after great apes have been granted membership, it might be wrong to ignore other species. Data from comparative and evolutionary studies in cognitive ethology and arguments based on evolutionary continuity also point to a broader view. As Degler rightly states, we must revisit Darwin and draw inspiration from 'his insistence upon the continuity between human and animal experience'.[13]

Acknowledgements - I thank Anne Bekoff, Lori Gruen, Susan Townsend, Carol Powley, Dale Jamieson, Bernard Rollin, Deborah Crowell and Robert Eaton for comments on this paper. The editors of this volume also made extremely valuable comments.