In that essay he presents an overview of the development of various philosophies of science, beginning with the view that science provides proven knowledge. The proving power of the intellect or the senses was questioned by the sceptics more than two thousand years ago, but they were browbeaten into confusion by the glory of Newtonian physics. Einstein's results again turned the table and now very few philosophers or scientists still think that scientific knowledge is, or can be, proven knowledge. Popper, Lakatos writes, has grasped the full implications of the collapse of the ideal of proven truth, and thus has arrived at the position that the proper scientific procedure is not to try to prove theories for that cannot be done in any case but to try to disprove them. One makes conjectures, in the Popperian program, and then specifies under what conditions the conjectures will be refuted.
Science consists of conjectural or refuted theories, never proven ones.
Unfortunately, Christians have not yet grasped that point, and are carrying on an argument that the scientists already admit they have lost. Many scientists and philosophers were unhappy with the conclusion that all scientific theories are unprovable, and sought to lower the standard from proved truth to probable truth. But even this retreat turned out to be insufficient. For the argument demonstrating that all theories have zero probability, I refer the reader to Gordon Clark's Philosophy of Science and Belief in God, pages 62-64. With the demise of probabilism a demise that could have been hastened if Augustine's demonstration that one cannot know what is probable unless one first knows what is certain falsificationism swept the field.