One of France's greatest theoretical scientists, Poincare will, with Konrad Lorenz and Albert Einstein, be associated with the early development of the special theory of relativity. He will perhaps become better known though for his ideas regarding the nature and process of science and scientific theories.
Jules Henri Poincare begins his theorizing after the discovery of non-Euclidean geometry leads him to the conclusion that, contrary to traditional belief, the axioms of geometry are not expression of logical truths, logical necessities, or empirical propositions.
Instead, they are simply definitions "in disguise" — they are decisions about how certain terms (like "point" and "line") will be used in order to accurately describe particular relationships. Different definitions could be chosen and thus create different geometries. The geometry which is chosen depends upon convenience and whichever set of relationships is most economical most fruitful.
Eventually Poincare comes to apply these ideas to physics as well. These ideas would come to be called "conventionalism" to reflect that idea that basic axioms or principles are "conventions" rather than logical or empirical truths. Poincare does not, however go so far as to argue that all empirical claims are simply matters of convention.
He argues instead that the physical sciences are attempts to describe a world which is independent of our minds; as such, it is possible for the physical sciences to be more or less accurate, even if many of its principles are conventions in nature.