"The wise man will not be content with the knowledge of things as they are, but will seek to know how they came to be so."

"I began to think whether there might not be a motion as it were in a circle."

"The circulation of the blood is a miracle of nature."

"Nature is a free and open book, to be read and understood by all who have the patience and the power to do so."

"It is not by words, but by facts and arguments, that we must seek for truth."