This study offers a comprehensive survey of the philosophy of language of Thomas Aquinas. Inside an anthropological framework, the acts of reason are understood as principles of language, with the act of judgement occupying a central place. Since reason discerns truth it is the basis for the differentiation of speech acts as well as for analysis of the concluding act of reason which progresses from the known to the unknown. It is oriented towards the acquisition and the communication of knowledge, in its paradigmatic form of demonstration as well as in the various forms of rhetorical and poetic speech. Thus, Thomas’s philosophy of language reaches its final goal in a theory of teaching and learning.