Taking as a starting point the discursive perspective, besides thinking about the specificity of the discourse produced as science, and therefore related and directed towards the circulation of knowledge, we propose to discuss the notions of production of knowledge and scientific practice in the writings by Michel Pcheux. We consider that the subject of knowledge production takes a subject position and inevitably shows their subjection not only to ideology and language, but also to theory and rule. In this perspective we try to regain some of the notions of science and subject of science, which we see as essential for the understanding of scientific practice, as well as indispensable to raise reflections about the relations among science, discourse and subject. The production of linguistic knowledge encompasses our research goal as a possibility to present the constitution of the subject category. We consider the historicity that permeates knowledge on discourse, subject and other components of externality, such as ideology and conditions of discourse production. This text presents partial research results, which are notes that contribute to the development of knowledge about how the production of knowledge and scientific practice occur in writings by Pcheux.