Worship the spirit of criticism. If reduced to itself it is not an awakener of ideas or a stimulant to great things, but, without it, everything is fallible; it always has the last word.

Science brings men nearer to God.

The greatest malfunction of spirit is to believe things.

How do you know that the incessant progress of science will not compel scientists to consider that life has existed during eternity, and not matter?

To know how to wonder and question is the first step of the mind toward discovery.

When I approach a child, he inspires in me two sentiments; tenderness for what he is, and respect for what he may become.

Every chemical substance, whether natural or artificial, falls into one of two major categories, according to the spatial characteristic of its form. The distinction is between those substances that have a plane of symmetry and those that do not. The former belong to the mineral, the latter to the living world.