Transcript: How do we test theories? There are two fundamental ideas. The first is the idea of induction. This was put into place by Francis Bacon, sixteenth century philosopher of science. Induction is the idea that we can generalize from a finite set of observations, or situations, or data, to a much broader range of situations. Science proceeds by induction but always has to recognize that the amount of data is limited and that data has errors attached. So induction is a process that can fail with insufficient data. The second idea is called falsification. It was put into place by the twentieth century philosopher of science, Karl Popper. The idea of falsification is that we make a theory or a hypothesis. We gather as much data as we can, and see if the data is confirming or falsifying the theory. In principle, if the data is falsifying the theory even by a modest amount or even only using a small amount of the data the theory must fall and must be replaced by a better theory. Once again observations have errors attached and are sometimes limited. So the idea of how a theory becomes falsified is a controversial issue amongst philosophers of science.