 He advocated conventionalism in other areas of science too, arguing that what we call the laws of nature (Newton’s laws, e.g., the principle of inertia) are neither empirical matters open to revision nor absolute truths but are well established results that have been elevated to the role of axioms in present scientific theories. They could be challenged, but only if a whole scientific theory was being challenged, not idly when some awkward observations were made. Faced with a satellite that did not seem to be obeying Newton’s laws one should, said Poincaré, consider some as-yet unnoticed force at work and not seek to re-write Newton. But a new theory can be proposed, based on different assumptions that rewrite a law of nature, because these laws are not eternal truths—we could never know such things. And if a new law were to be proposed, simplicity and not only empirical fit will be taken into account as one chooses between the new and the old.