AbstractAfter a few considerations on the limited value of reasoning by analogy, the author distinguishes between analogy, homology and model, as illustrated by electro‐pneumatic, electro‐mechanical and electro‐thermic homologies. On the other hand, there exist numerous models of a same process: mathematical and symbolic models, graphic models, analogic and numeric models. The paper ends with remarks on the limits and the applications of models, namely in adaptative systems, as well as on their philosophical