One aspect of the concept of man as a rational animal is an implicit mental model that defines human beings as inherently aggressive and violent. This section contains a critical analysis of a few of the arguments that are often used to promote this idea: that we have an instinct for aggression and territorialism, and that we have ‘violent brains’. An argument that is often put forward to justify war and other acts of violence is that they are determined by a 'killer instinct' in human beings. Some ethologists –scientists who study animal behavior– have proposed the existence of human instincts for territorialism, aggression and war, which they suggest could have been inherited during our evolution from other animal species.
These few examples suffice to show that we are surrounded by diverse cultures of cooperation and peace which, while plentiful and pervasive, are largely obscured by the dominant culture of selfishness and violence. In fact, it is because of these elements of mutualism that humanity has been able to preserve its cohesion and vitality. They offer a rich reserve of non-adversarial strategies and resources for sociocultural change. Finally, they offer indisputable proof of the possibility of a different world, as per the famous truism of the renowned social scientist and peace activist Kenneth Boulding: “Whatever exists is possible.”