I will propose an epistemological study of the genesis of some theories in physics, strengthening the role of analogical thinking in those creative processes. For that purpose, I will consider a subject/object interaction viewpoint, as it is taken in Piaget's genetic epistemology, directed towards the assimilation/accommodation equilibrium. In this framework, some interesting examples will be analyzed in the history of physics. I want to show that the distinction between analogical mapping and analogical reasoning must be clearly drawn. We can not have a coherent analogical reasoning without mapping, but mapping is not sufficient to ground a coherent reasoning with new knowledge. Thus, coherentism is the main epistemological perspective we need, and cyclical diagrams will be used to present and explain the new theoretical consequences coming from all that.