First, I noticed that the strong certainty people generally give to these proofs comes from the fact that they are clearly understood according to the principles I had already established.
On 23 December 1863, after returning from dining out and before dressing for bed, he suffered a stroke. He was found dead in his bed the following morning.
And, in the first place, I observed, that the great certitude which by common consent is accorded to these demonstrations, is founded solely upon this, that they are clearly conceived in accordance with the rules I have already laid down.