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nature of tliat influence, the relation we are now speaking of 
as the third must therefore be admitted to be as palpable to 
reason as the other two ; and we call it force. 
Of the three relations, time, place, and force, one of them — 
namely, time — never has a constant identity. Time is inces- 
santly changing ; but inasmuch as in passing away it sub- 
stitutes a reproduction of itself, the change in identity vir- 
tually leaves tLe relation of time unaltered. The second 
relation, place, can only be disturbed by motion, which, how- 
ever slight, changes one event by substituting another. If 
motion in the things related could be an accidental occur- 
rence, we might have new events by accident ; but as that 
cannot be, the system of nature would, if there were only 
tw’O relations of time and place, be a perpetual reign of 
unbroken sameness. It is only by the production of motion 
by the third relation, force , that its associates, time and place, 
have any influence in causing physical events ; otherwise 
impotent, they are thereby, as I have said, made productive. 
Force inseparably appertains to the materials whose relations 
to one another cause events by undergoing change. Con- 
sequently we have, as the cause of events, not force alone, 
nor place alone, nor time alone, but all three together , each 
determining by its existing relation to the materials what the 
influence on them shall be ; there must be force to act on 
them, time must have the . relation of being present, and 
place must determine what depends upon relative position. 
At this point the system I am describing furnishes a truth 
most extensively borne out by observation — namely, that if we 
neglect the ideas of antecedence and subsequence , the expres- 
sions cause and effect become interchangeable, because all the 
relations between them, with the exception of time, are 
minutely reciprocal and equally consequential in one direction 
as in the other, by which is shown the necessity of taking the 
relation of time into consideration. Cause must in some 
slight measure occur before its effect, and so far one is dif- 
ferent from the other ; but during the time that they co-exist 
each is the cause of the other. Attraction may possibly move 
the effect towards its cause, or the cause towards its effect ; or 
the two may be moved simultaneously ; and, however slight 
the change of place may be in either, the movement will be 
productive of a new event, or fact, each originating its own 
series of consequences. For want of recognizing the several 
elements of cause, physical science has been involved in 
serious mistakes, being made responsible for what mechanical 
writers call accelerating forces, entirely unknown to nature ; 
for when moral power takes upon itself to become physical, it 
