How did Latin medieval philosophers understand dialectics, especially theoretical dialectics? What were its scope, goals and tools according to Western medievals? This paper aims at offering a general account of what theoretical dialectics is according to Latin medieval philosophers by considering how commentators of Aristotle’s Topics (from mid-thirteenth to the fifteenth century) dealt with some key dialectical notions such as probabilitas, disagreement, opinion and dialectical proof. The first section of the paper presents the meanings of ‘dialectics’ according to some relevant Latin authors from the Late Ancient period to the eleventh to twelfth century. The second section introduces the main features of theoretical dialectics and its relationship with the scientific method and science in the Latin speaking world. The third section considers the epistemology and semantics of probabilis/probabilitas elaborated by Latin medieval commentators of the Topics and the relation between the probable and truth. The fourth section considers the social dimension of dialectics, e.g., disagreement, and the main element of dialectical discussions, namely dialectical questions and propositions. The fifth and last section delineates the logico-semantic and epistemic features of dialectical proof, with a special emphasis on the role of topics in dialectical proofs.