Our Western society has been much shaped by scientific thought and discoveries. We not only depend practically on science in our ways of living. Our thinking and attitudes are also shaped by the theories and methods of science. The overwhelming intellectual and practical successes of science that lie behind this impact of science on our culture have led some people to think that there are no real limits to the competence of science, no limits to what can be achieved in the name of science. Or, if there are limits to the scientific enterprise, the idea is that science, at least, sets the boundaries for what we humans can ever achieve or know about reality. There is nothing outside the domain of science, nor is there any area of human life to which science cannot successfully be applied. This view (or similar views) has sometimes been called scientism. (It has also been labelled scientific naturalism or scientific materialism. I will, however, try to show why we should not attribute the same meaning to these three terms.)