EVOLUTION AND THE PRESENT AGE 259 
my meaning, let us consider a few familiar incidents 
in the history of scientific discovery. 
Every achievement in science has consisted in point- 
ing out likenesses that had before remained undetected. 
Every scientific inquirer is on the lookout for such 
likenesses. If the likeness assigned be a wrong one, 
we have false science. For example, in order to ac- 
count for the movement of the starry heaven from east 
to west, some of the ancient astronomers fancied that 
the earth was encompassed by a revolving crystalline 
sphere in which countless points of light were set for 
the purpose of illuminating the earth during the sun’s 
absence. Because the stars preserve the same relations 
of position, one to another, they were supposed to be 
fastened on the inside of this sphere, and in accordance 
with this theory we have such phrases as “fixed stars” 
and “firmament.” Here men sought to explain the un- 
known by analogies with the known, but the likeness 
turned out to have been entirely mistaken. The merit 
of the Newtonian astronomy was that it found in the 
known world the correct likeness to that which was 
going on in the unknown world. Copernicus had 
shown that it is not the earth, but the sun, which forms 
the centre of the planetary system; Kepler had gone 
on to show that the planets revolve about the sun in 
ellipses and in accordance with certain laws of motion 
which he described ; the question remained, Why do 
the planets move in this way? Does each one have a 
guardian. angel to pull it or push it along, or must we 
perhaps give up the case without any explanation? 
Then Newton came and showed that what happens in 
the sky is just what happens on the earth. The earth 
pulls the moon exactly as it pulls the falling apple; 
