The article discusses various deliberations on the relationship between 'hen' and 'monas' supposed by Philolaus of Croton. In this analysis, particular attention is paid to 'kosmos', 'eonta', 'arithmos' and 'arche'. Thus, it became necessary to refer to Philolaus's predecessors. The cohesion of thought of Philolaus and two other philosophers, Parmenides and Melissos, as well as Heraclites, Anaximenes and Pythagoras has been maintained. The main aim of the analysis is the question of the possibilities of interpretation of the 'archai'. The results have shown that monada cannot be a mathematical project. What is it then? The concluding part of the article refers to Archippos, Lyzis and Opsimos. Are the suppositions based on Philolaus' texts going to be confirmed by his successors or are they going to be categorically rejected?