The methodology of the physical sciences comprises two components:

1. the invention of laws;

2. the demonstration of laws.

To find the laws that govern phenomena, we must begin with observation, the simple ascertaining of facts as they are. Before explaining a phenomenon, we must understand it precisely, and this is the goal of observation.

In the physical sciences, observation involves the use of the senses, whose reach is extended by various instruments. The observant individual should have four characteristics: attentiveness, intelligence, exactitude, and impartiality.

To say that an observer should be attentive is to say a bit more than that he should merely observe. He should neglect no detail whatsoever and, without being distracted, pay attention to everything that occurs before him. For observation to be a fruitful activity, the observer must also be sufficiently intelligent to distinguish important from less important facts. Finally, the observer shouldn't add to or subtract from the phenomena observed and – as completely as possible – should embrace the role of faithful witness. He must remain impartial, for if he doesn't, he risks seeing what he wants to see rather than what's really there.

Observation reveals facts as they are, but this still leaves us far from the discovery of laws. For laws aren't inscribed in things from which their secrets must be wrested. It's up to us to extract laws from the material provided by observation, and here invention plays an important role.