Chapter 15 is separated into three parts. It first traces the origin of the dialectic theory proposed by philosopher Hegel, then discusses its development and use in the field of philosophy, and finally criticizes its limitations.

1. Dialectic Explained

The chapter begins with a quote by French philosopher René Descartes: “There is nothing we can imagine, however absurd or incredible, that has not been maintained by one philosopher or another” (312).

Popper believes this to be true and adds that this applies not only to philosophy, but to any field involving human thought and enterprise, such as physics, technology, engineering, and politics. This is because the process of acquiring knowledge is one of trial and error: People that wish to solve a problem will test various methods until they approach a solution. Their chances of success depend on the number and variety of the trials they undertake, and the more numerous and diversified these tests are, the higher the likelihood of solving the problem. This is the fundamental process of adaptation used by living organisms.

There is another method by which knowledge might be advanced. When people encounter a problem and propose a theory, they either cling to the theory for as long as they can, or they fight against it once they realize it is no longer viable.