A scientific theory is an attempt to bind together in a systematic fashion the knowledge that one has of some particular aspect of the world of experience. The aim is to achieve some form of understanding, where this is usually cashed out as explanatory power and predictive fertility.
Explanation therefore is a matter of showing how things happened because of the laws of the theory.
Prediction is a matter of showing how things will happen in accordance with the laws of the theory. Most significant is the fact that really successful theories bind together information from many hitherto disparate areas of experience, thus exhibiting what the philosopher William Whewell characterized as a ' consilience of inductions'. In recent years, this picture of theories has come under some considerable attack. Moreover, while such a theory as Darwin's certainly has some predictive power, it can hardly be said that this is a compelling attraction. Supporters of this 'semantic view' of theories argue that theories should not be seen as overall systems trying to cover, at one move, major areas of experience.