As we have seen, originally 'science' meant 'certain and indubitable knowledge'; hence Locke's assertion that natural philosophy could never be a science.! Science had also been contrasted with art where 'science' was the word for theoretical truth and 'art' stood for practical and traditional skills. The study of nature and the search for explanations of events was called 'natural philosophy' because, at first, the study of what could be observed in the world was seen as part of a more general inquiry into what human beings could know and about how they should live. It was part of a search for general understanding, and therefore it was a part of philosophy - seen as the love of wisdom. Our present view of science as a more limited subject with a characteristic methodology based on observation and planned experiment, on critical interpretation and generalization, and on conjectures leading to hypotheses and to explanatory theories, has developed in the last three hundred years. Hence the change from natural philosophy to science represents more than a change of name. It shows a change in attitude to the nature of empirical knowledge and to how it is to be found.