108 
much better. For we have forgotten to allow for the earth’s 
motion in its orbit. This being some 68,000 miles per hour, it 
follows that, assuming that time to be midday, he is moving, 
not at the rate of 1,000 miles per hour to the east, but at the 
rate of 67,000 miles per hour to the west. Nay, not even now 
have we discovered the true rate and the true direction of his 
movement. With the earth’s progress in its orbit, we have to 
join that of the whole solar system towards the constellation 
Hercules ; and when we do this, we perceive that he is moving 
neither east nor west, but in a line inclined to the plane of the 
ecliptic, and at a velocity greater or less (according to the time 
of the year) than that above named. To which let us add, that 
were the dynamic arrangements of our sidereal system fully 
known to us, we should probably discover the direction and 
rate of his actual movement to differ considerably even from 
these. How illusive are our ideas of motion, is thus made 
sufficiently manifest. That which seems moving proves to be 
stationary ; that which seems stationary proves to be moving ; 
while that which we conclude to be going rapidly in one 
direction, turns out to be going much more rapidly in the 
opposite direction. And so we are taught that what we are 
conscious of is not the real motion of any object, either in its 
rate or direction ; but merely its motion as measured from an 
assigned position, — either the position we ourselves occupy or 
some other. Yet in this very process of concluding that the 
motions we perceive are not the real motions, we tacitly assume 
that there are real motions.”* 
21. I affirm that all the motions mentioned here are real 
motions, and not mere illusions, or apparent motions. They are, 
doubtless, motions in different directions, but not the less real on 
that account. It might be difficult to determine at any given 
moment the absolute positions of the ship, captain, and earth, 
in reference to some particular far-off world ; but that diffi- 
culty is the result of their each moving at the same time. 
The captain, while walking the deck, may keep the same 
position relatively to an object on shore ; but had he not been 
moving on the ship at the same time the ship was moving, 
on a moving earth, that relative position would have been at 
once altered. Mr. Spencer in his illustration makes very clear 
how difficult it would be to ascertain the rate at which any one 
of the objects moved, or the actual direction ; but the fact of 
a real motion in some direction and at some rate is beyond all 
controversy. It is, no doubt, impossible to understand why a 
* “ First Principles,” p. 54. 
