The purpose of the article is to present the ideas that the Austrian physicist Ludwig Boltzmann (1844-1906) developed on the role of classical mechanics in physics. He had elaborated them at a time when classical mechanics began to be considered as not being any more the ground for all other physical theories. Boltzmann never accepted this conclusion. He rejected it, developing at the same time some ideas on the epistemological nature of scientific theories. According to him, scientific theories are representations of natural phenomena.