In the Sigillus sigillorum (The seal of seals, published in London in 1583), Bruno develops two parallel lines of thought, one on ontology and one on epistemology. Within the first line of thought he delineates the metaphysical structure of the universe and its process of individuation, called descension; the epistemological line of thought explains how it is possible for man to ascend within that structure. Bruno insists that these two topics, descension and ascension, must exist in conformity, and, accordingly, that they must be conceived of in a uniform manner. In this article I analyse one particular notion in the Sigillus which is essential to both of these two parallel lines of thought, namely the notion ‘contractio’, a Latin term whose basic meaning is a process of drawing together.