410 
mankind. But we shall be left just as unscientific as before. 
In our search for something real and absolute, we are to 
abandon all terms which express only relative motion. But 
the rainbow recedes before us. The sun rises and sets no 
longer, and the earth revolves on its own axis, and in its orbit 
round the sun as a fixed centre. But of this fixed centre 
it has to be said in its turn, “ And yet it moves. Neither 
the earth is now to revolve round the sun, nor the. sun round 
the earth, but both alike around a fixed invisible point between 
them. Here again we find no rest. Herscliel s discovery alters 
and disturbs our last conclusion. The earth and planets no longer 
move in ellipses around a common invisible centre, but travel in 
complicated corkscrews, or spirals, through empty space. And 
we have no assurance that this stage is final,, and that all the 
stars, from which the sun’s motion has been inferred, may not 
be travelling together towards some more distant point or centre 
in the depths of infinite vacuity. 
22. These changes all assume that there is some absolute motion, 
which alone is scientifically true. But is this certain ? May we 
not be sacrificing what is certain and real to a mere shadow, instead 
of exchanging a series of fictions for reality • Is there, after all, 
such a thing as absolute motion ? The common impressions are 
given by Newton in his scholium in these words : — 
“ Absolute space in its own nature, without regard to anything external, 
remains always similar and immovable. Relative space is some movable 
dimension or measure of the absolute space, which our senses determine by 
its positions to bodies, and which is vulgarly taken for immovable space. 
Absolute and relative space are the same in figure and magnitude, but they 
do not remain always immovably the same. For if the earth, for instance, 
moves, a space of our air which, relatively in respect of the earth remains 
always the same, will at one time be one part of absolute space, at another 
time it will be another part. . . Absolute motion is the translation of a 
body from one absolute place into another, and relative motion from one 
relative place into another. Thus, in a ship under sail, the relative place is 
that part of the ship which the body possesses. Relative rest is the con- 
tinuance in the same part of the ship, or its cavity. But real, absolute rest, 
is the continuance of the body in the same part of the immovable space, in 
which the ship and all that it contains is moved.” 
23. Newton then proceeds to put the case of a sailor, walking 
on a ship’s deck from west to east, while the ship sails ten times 
as fast westward, and the earth 10,000 times as fast from, west to 
east. In Mr. Spencer’s First Principles an exactly similar case 
is proposed, to prove that absolute space and motion are inconceiv- 
able. The conclusion drawn is in these words : — 
