In an introductory part, a number of aspects in the attitude of man towards animals and nature are distinguished, such as an economic, a knowledge, an emotional, a moral, a religious and an ethical aspect. Shifts in the intensity and priorities of these aspects, in the emphasis put on them during various cultural periods, are plainly perceptible and have been so particularly during the past few years: increasing exploitation of animals and nature on the one hand and an increase in sensitivity on the other. Various protective movements have emerged and become active in this sphere during the past 150 years: first, protection of animals, then conservation of nature and, more recently, environmental protection. A special aspect of the exploitation of animals consists in intensive livestock production which has grown considerably during the last few decades. Strong objections to certain features of this system have not only been raised by national and international societies for the prevention of cruelty to animals but also by ethologists. Admittedly, it is difficult to lay down exact criteria of animal welfare (which, for that matter, also is true of criteria of human welfare) but it is essential to a systeem of values which is becoming increasingly sensitive that efforts should be made to alter the current system of intensive livestock production with the aid of the various sciences closely associated with this system as well as by enlightenment of consumers. The question as to what we are allowed to do with animals and that of where the shifting limits of necessity lie are becoming increasingly relevant from the points of view of ethics and science.