As is well known, taṣawwur and taṣdīq, conceptualization and assent, are essential notions in the epistemology of Arabo-Islamic philosophy. Conceptualization amounts to the definition of an object of knowledge, and assent to the recognition, via some kind of reasoning, that this definition is true. One of the authors who dealt with both topics in greatest depth was al-Fārābī, whose oeuvre exerted a profound influence on Ibn Bājja. This article analyzes the materials on taṣawwur and taṣdīq found in Ibn Bājja's notes regarding al-Fārābī's writings on logic and scientific method, namely the glosses to Kitāb al-Burhān. The analysis shows, on the one hand, that he understood perfectly the importance of both terms in al-Fārābī's construal of Aristotle's scientific method; and on the other, that he used them to deal with human thought processes. Indeed, conceptualization and assent were essential notions for Ibn Bājja, and underlie some of his best-known works.