Determinism is the theory that all things in nature develop according to a predetermined pattern. For example, humans and animals are merely the product of their genetic makeup and have very little freedom to achieve anything beyond what is already innate. In the past, philosophers have often viewed the world through a theological or naturalistic deterministic lens; though the practice should be considered outdated, Popper points out that historicists such as the Marxists and defenders of Hegel’s dialectical method still perpetuate this same ideology.

Dogmatism is the practice of stubbornly clinging to an idea or fact. It often manifests as an intolerant attitude, especially when presented with alternate or incompatible information. Popper condemns dogmatism for its inability to accept criticism and falsification, arguing that clinging to an idea and refusing all criticism of it halts scientific progress.

Doxa designates any subjective opinion held by individuals. It is inexact and lacks objectivity. It is used in contrast to episteme, which describes tried and true scientific facts.