Geometry, which should only obey Physics, when united with it sometimes commands it. If it happens that the question which we wish to examine is too complicated for all the elements to be able to enter into the analytical comparison we wish to make, we separate the more inconvenient [elements], we substitute others for them, less troublesome but also less real, and we are surprised to arrive, notwithstanding a painful labour, only at a result contradicted by nature; as if after having disguised it, cut it short or altered it, a purely mechanical combination could give it back to us.

I am worn out by the insults and vexations that this work brings down on us.

Gaming is the destruction of all decorum; the prince forgets at it his dignity, and the lady her modesty.

The true system of the World has been recognized, developed and perfected...Everything has been discussed and analysed, or at least mentioned.

There are only two kinds of certain knowledge: Awareness of our own existence and the truths of mathematics.

Algebra is generous; she often gives more than is asked of her.

Just go on..and faith will soon return.