Famous quotes containing the words principal and/or series:
“There are three principal means of acquiring knowledge available to us: observation of nature, reflection, and experimentation. Observation collects facts; reflection combines them; experimentation verifies the result of that combination. Our observation of nature must be diligent, our reflection profound, and our experiments exact. We rarely see these three means combined; and for this reason, creative geniuses are not common.”
—Denis Diderot (1713–1784)
“Galileo, with an operaglass, discovered a more splendid series of celestial phenomena than anyone since.”
—Ralph Waldo Emerson (1803–1882)