This paper deals with Husserl’s idea of pure logic as it is coined in the Logical Investigations (1900/1901). First, it exposes the formation of pure logic around a conception of completeness (Sect. 2); then, it presents intentionality as the keystone of such a structuring (Sect. 3); and finally, it provides a systematic reconstruction of pure logic from the semiotic standpoint of intentionality (Sect. 4). In this way, it establishes Husserlian pure logic as a phenomenological epistemology of mathematical logic.