This book describes some instants of the conceptual history of mathematics and physics, yet the philosophical arguments of the ideas involved in some of them, for example the roots geometry, of analysis, of Galois theory, of vectors, space and physical approach of the continuum. They are presented in a technical language but with a philosophical colour trying to make their meaning easier for students and for those who are interested in the meaning of all these things. As meaning we say is "the substantive content that gives a reasonable coherence to a concept or an action".