"The total acceleration in a given time is proportional to the force. For if several equal forces act in the same direction on the same body in the same direction, each produces its effect independently of the others."
"In all scientific procedure we begin by marking out a certain region or subject as the field of our investigations. To this we must confine our attention, leaving the rest of the universe out of account till we have completed the investigation in which we are engaged."
"In future... when we use the word acceleration without qualification, we mean... the rate of acceleration."
"The following statement... appears... and more capable of application to particular cases: "The difference between one event and another does not depend on the mere difference of the times or the places at which they occur, but only on differences in the nature configuration or motion of the bodies concerned." It follows from this, that if an event has occurred at a given time and place it is possible for an event exactly similar to occur at any other time and place."
"Relative, apparent, and common time is duration as estimated by the motion of bodies, as by days months and years."
"The idea of Time in its most primitive form is probably the recognition of an order of sequence in our states of consciousness."
"A knowledge of the configuration of the system at a given instant implies a knowledge of the position of every point of the system with respect to every other point at that instant."