The science that illuminates the mind the most, that makes it exact and broad, and which consequently must prepare the study of all other sciences, is metaphysics.

Today in France, this science is so marginalized that our thought will surely appear paradoxical to many readers. I confess that I would have shared the same opinion in the past. Among philosophers, metaphysicians seemed to me the least wise: their books did not teach me anything; I almost everywhere found phantoms and considered it a crime against metaphysics the errors of those who served it.

Therefore, I wanted to dispel this illusion and refer to the cause of the errors; the most useful among them were also the most distant from the truth. As soon as I became aware of the precarious paths they had followed, I believed I discerned the path which I should open.

It seemed to me that both in metaphysics and in ethics, one could think with the precision that geometry determines; to acquire, like geometers, precise ideas; to define, like them, the meaning of expressions in a stable and accurate manner; finally, to impose on oneself, possibly better than them, a simple and easy arrangement to achieve clarity.