A Hypothesis taken together with some Auxiliary assumptions to deduce, according to the laws of logic, a prediction that can be directly verified or falsified in experience. Every instrument and experiment assumes a body of theory in order to arrive at an interpretation of the data. When a experimental result fails to verify the prediction, it may be these auxiliary assumptions that have to be revised instead of the hypothesis. Scientific Progress on this view involves the accumulation of verifying results in experiments. As these grow in number we can be more confident of our hypothesis, until it finally is verified so many times it becomes a law, taken for granted as true.
Science progresses by the gradual accumulation of data.
To explain an event you simply find some general covering law that would have allowed you to predict it. Sometimes this is called post-diction. One explains an event by coming up with a set of laws that would have allowed one to predict the event before-hand. By showing how the event wold have been rendered necessary by these physical laws, one explains the event. On this view, there is logic of Justification , but there is no logic of Discovery .