Surely, God could have caused birds to fly with their bones made of solid gold, with their veins full of quicksilver, with their flesh heavier than lead, and with their wings exceedingly small. He did not, and that ought to show something. It is only in order to shield your ignorance that you put the Lord at every turn to the refuge of a miracle.
Notes in a copy of Jean-Baptiste Morin's "Famous and ancient problems of the earth's motion or rest, yet to be solved" (published 1631), as quoted in The Crime of Galileo (1976) by Giorgio De Santillana, p. 167