(1.) The nature around us is colourful and diverse. It is but natural that man saw, studied and unravelled nature and its laws. The great physicists Dr.R.P.Feynman gave a wonderful description of what is 'understanding the nature'. Suppose we do not know the rules of chess but are allowed to watch the moves of the players. After some time we make out some of the rules. With the knowledge of these rules we may try to understand why a player played a particular move. However, this may be a very difficult task. Even if we know all the rules of chess, it is not so simple to understand all the implications of a game in a given situation and predict the correct move. Knowing the basic rule is, however, the minimum requirement if any progress is to be made.
(2.) By partially watching a game we may guess at a wrong rule. The experienced player may make use of a rule for the first time and the observer of the game may get surprised. Because of the new move some of the rules guessed at may prove to be wrong and the observer will frame new rules.
(3.) Physics goes the same way. Events in nature are like the moves of a chess game. We guess the basic rules according to which the events take place. We may come across new events which do not follow the rules guessed earlier. Therefore, we declare the old rules inapplicable or wrong and discover new rules.