Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.

It is always advisable to perceive clearly our ignorance.

Blushing is the most peculiar and most human of all expressions.

On the ordinary view of each species having been independently created, we gain no scientific explanation.

To kill an error is as good a service as, and sometimes even better than, the establishing of a new truth or fact.

The more one thinks, the more one feels the hopeless immensity of man's ignorance.