What is critical rationalism?

Critical rationalism holds that there is objective truth and it is possible for people to learn about it. You learn about how the world works by making guesses and then criticising the guesses. You never have any guarantee that you have reached the truth although you may make progress toward it through critical discussion.

Most epistemologists make a lot of fuss about certainty, but this is largely irrelevant to making progress. What is relevant to making progress is getting rid of bad ideas and proposing replacements that fix the flaws in your previous ideas.

The focus on certainty has done a lot of damage to epistemology leading to a lot of subjectivist nonsense. For an extended discussion of this problem, see "Realism and the Aim of Science" by Popper, Chapter I. Other material worth reading on critical rationalism includes "On the sources of knowledge and of ignorance" in Popper's book "Conjectures and Refutations", the title essay in Popper's book "The Myth of the Framework", as well as chapters 3 and 7 in "The Fabric of Reality" by David Deutsch.

If you are interested in discussing Popper further with people who have deep knowledge of Popper, you may want to consider the Fallible Ideas discussion group.

Critical rationalism is the view propagated by Popper.

Popper does not give up the concept of truth.

His first point is, that we cannot prove general theorems in science, because we always have only finitely many observations. The next observation could refute the statement. Hence Popper gives up proving general theorems in science.

According to Popper our scientific theorems are hypotheses. One should create hypotheses which are testable. A test can confirm or refute a hypothesis. In the latter case, the hypothesis is false and we need a better hypothesis. But even a confirmed hypothesis is not proved. We do not know whether it is true. Hence Popper replaces proof by falsifcation.

By eliminating false hypotheses we hope to approach truth, which is considered a limit term. Pointedly formulated by Gerhard Vollmer: "We err upwards."

Certainty is the personal feeling to have true knowledge. It is a subjectice term and does not guarantee truth.