Ugolino (c. 1380-1457) wrote one of the largest treatises on music theory in the first half of the fifteenth century. This work, the "Declaratio musicae disciplinae," is comprised of five books that cover everything a musician of the era would need to know, from plainchant to harmonic proportions, from musica practica to musica speculativa. However, the treatise has received contradictory interpretations by modern scholars, some viewing it as mainly practical, others as mainly theoretical. I argue that in Book 2, which deals with counterpoint, Ugolino crystallizes the relationship between theory and practice, while offering distinctive contrapuntal practices. Ugolino presents a unique view music's place in the structure of knowledge, one which is highly dependent on Aristotelian philosophy. He posits that music is a science and that it is a branch not of mathematics, as it had traditionally been categorized, but of natural philosophy. This viewpoint shapes the entire treatise and is evident in the book on counterpoint. There, he presents an Italian tradition of teaching counterpoint known as the "regola del grado." Ugolino is the first author to present this tradition entirely in Latin. In addition, he offers an unusual description of musica ficta. In it, he presents a diagram, the "duplex manus," that mixes together both musica recta and musica ficta. Ugolino's work suggests that theory and practice, although arranged hierarchically, need not be in conflict, and that a treatise such as his can be both eminently practical and highly theoretical.