We must alter theory to adapt it to nature, but not nature to adapt it to theory.‎

I do not ... reject the use of statistics in medicine, but I condemn not trying to get beyond them and believing in statistics as the foundation of medical science. ... Statistics ... apply only to cases in which the cause of the facts observed is still [uncertain or] indeterminate. ... There will always be some indeterminism ... in all the sciences, and more in medicine than in any other. But man's intellectual conquest consists in lessening and driving back indeterminism in proportion as he gains ground for determinism by the help of the experimental method.

Descriptive anatomy is to physiology what geography is to history, and just as it is not enough to know the typography of a country to understand its history, so also it is not enough to know the anatomy of organs to understand their functions.

It has often been said that, to make discoveries, one must be ignorant. This opinion, mistaken in itself, nevertheless conceals a truth. It means that it is better to know nothing than to keep in mind fixed ideas based on theories whose confirmation we constantly seek, neglecting meanwhile everything that fails to agree with them.

But while I accept specialization in the practice, I reject it utterly in the theory of science.

Laplace considers astronomy a science of observation, because we can only observe the movements of the planets; we cannot reach them, indeed, to alter their course and to experiment with them. "On earth," said Laplace, "we make phenomena vary by experiments; in the sky, we carefully define all the phenomena presented to us by celestial motion." Certain physicians call medicine a science of observations, because they wrongly think that experimentation is inapplicable to it.

The goal of scientific physicians in their own science ... is to reduce the indeterminate. Statistics therefore apply only to cases in which the cause of the facts observed is still indeterminate.