Although in one sense the title is misleading due to its one-sidedness, On Certainty has rightly been characterized as a work on epistemology, a work that inaugurates new lines of thought on the concepts of knowledge, doubt, and the justification of beliefs.

Moreover, independently of its contribution to articulating epistemological positions, the book clearly stands as Wittgenstein’s third masterpiece (after the Tractatus and the Philosophical Investigations), extending and broadening Wittgenstein's reflections on language, logic, and human life.

The wealth of observations, the philosophical fertility of the questions and different answers, as well as the variety of themes addressed in these notes, not only affirm such a characterization but also allow the reader to follow the trajectory of a great philosopher's thought.

These notes address the problematic of idealism and skepticism, the concept and role of doubt, the meaning of knowledge and its grounding, the concept of justification and the documentation of empirical beliefs, as well as many other epistemological issues, beyond the emblematic notion of certainty, which occupies a significant portion of the book's philosophical inquiries.