“The essays and lectures of which this book is composed are variations upon one very simple theme—the thesis that we can learn from our mistakes. They develop a theory of knowledge and of its growth.”

This quote underlines the main premise of the book: Human knowledge can grow using the correct means and by embracing The Importance of Refutation and Criticism. Popper fundamentally believes that learning from mistakes and understanding how problems are created and solved helps science progress. It is also the objective of the book to explore by what means this process of analysis and growth can be accomplished with the greatest possible accuracy.

“Criticism of our conjectures is of decisive importance: by bringing out our mistakes it makes us understand the difficulties of the problem which we are trying to solve. This is how we become better acquainted with our problem, and able to propose more mature solutions: the very refutation of a theory—that is, of any serious tentative solution to our problem—is always a step forward that takes us nearer to the truth.”

The Importance of Refutation and Criticism is at the core of Popper’s thesis on scientific growth. In this quote, he explains why attempting to refute a theory helps to solve problems faster. This is because finding nothing but confirmations is unproductive to understanding the limits of a theory—only refutations help refine and improve them.

“It was precisely this fact—that they always fitted, that they were always confirmed—which in the eyes of their admirers constituted the strongest argument in favour of these theories. It began to dawn on me that this apparent strength was in fact their weakness.”

Popper explains how he came to doubt the scientific status of certain theories, such as the Marxist theory of history, the Freudian theory of psychoanalysis, and the Adlerian theory of individual psychology. He realized that admirers of these theories see in every scenario a confirmation of their views instead of embracing The Importance of Refutation and Criticism to further refine their theories.