With the Earth's progress in its orbit, we have to join that of the wholeSolar system towards the constellation Hercules. When we do this, we perceivethat he is moving neither East nor West, but in a line inclined to the planeof the Ecliptic, and at a velocity greater or less (according to the timeof the year) than that above named. And were the constitution of our SiderealSystem fully known, we should probably discover the direction and rate ofhis actual movement to differ considerably even from these. Thus we are taughtthat what we are conscious of is not the real motion of any object, eitherin its rate or direction, but merely its motion as measured from an assignedposition -- either our own or some other. Yet in this very process of concludingthat the motions we perceive are not the real motions, we tacitly assumethat there are real motions. We take for granted that there is an absolutecourse and an absolute velocity and we find it impossible to rid ourselvesof this idea. Nevertheless, absolute motion cannot even be imagined, muchless known. Apart from those marks in space which we habitually associatewith it, motion is unthinkable. For motion is change of place; but in spacewithout marks, change of place is inconceivable, because place itself isinconceivable. Place can be conceived only by reference to other places;and in the absence of objects dispersed through space, a place could be conceivedonly in relation to the limits of space; whence it follows that in unlimitedspace, place cannot be conceived -- all places must be equidistant from boundarieswhich do not exist. Thus while obliged to think that there is an absolutemotion, we find absolute motion cannot be represented in thought.

Another insuperable difficulty presents itself when we contemplate thetransfer of Motion. Habit blinds us to the marvellousness of this phenomenon.

Familiar with the fact from childhood, we see nothing remarkable in the abilityof a moving thing to generate movement in a thing that is stationary. Itis, however, impossible to understand it. In what respect does a body afterimpact differ from itself before impact? What is this added to it which doesnot sensibly affect any of its properties and yet enables it to traversespace? Here is an object at rest and here is the same object moving. In theone state it has no tendency to change its place, but in the other it isobliged at each instant to assume a new position. What is it which will forever go on producing this effect without being exhausted? and how does itdwell in the object? The motion you say has been communicated. But how? --What has been communicated? The striking body has not transferred a thingto the body struck; and it is equally out of the question to say that ithas transferred an attribute. What then has it transferred?

Once more there is the old puzzle concerning the connexion between Motionand Rest. A body travelling at a given velocity cannot be brought to a stateof rest, or no velocity, without passing through all intermediate velocities.

It is quite possible to think of its motion as diminishing insensibly untilit becomes infinitesimal; and many will think equally possible to pass inthought from infinitesimal motion to no motion. But this is an error. Mentallyfollow out the decreasing velocity as long as you please, and there stillremains some velocity; and the smallest movement is separated by an impassablegap from no movement. As something, however minute, is infinitely great incomparison with nothing; so is even the least conceivable motion infiniteas compared with rest.

Thus neither when considered in connexion with Space, nor when consideredin connexion with Matter, nor when considered in connexion with Rest, dowe find that Motion is truly cognizable. All efforts to understand its essentialnature do but bring us to alternative impossibilities of thought. §18. On lifting a chair the force exerted we regard as equal to thatantagonistic force called the weight of the chair, and we cannot think ofthese as equal without thinking of them as like in kind; since equality isconceivable only between things that are connatural. Yet, contrariwise, itis incredible that the force existing in the chair resembles the force presentto our minds. It scarcely needs to point out that since the force as knownto us is an affection of consciousness, we cannot conceive the force to existin the chair under the same form without endowing the chair with consciousness.

So that it is absurd to think of Force as in itself like our sensation ofit, and yet necessary so to think of it if we represent it in consciousnessat all.

How, again, can we understand the connexion between Force and Matter?