The present teaching of Science is that Force is the result of the motion of the Particles of Substance, and, of course, originates from _within_, rather than from without. It is true that Motion may be communicated to a body by means of another body in Motion imparting the same to it, but that does not alter the case, for the Original Motion came from the movement and vibration of the Particles of Substance, although it may have passed through many stages of transformation, change and transmission in its progress. The only exception to the rule is Gravitation, which is a form of Force, the nature of which is unknown to Science, although its laws of operation, etc., are understood. We shall learn some new facts about Gravitation in the forthcoming chapters of this book. It will be well for us to remember _this_ fact, in our consideration of Force and Motion--that Force and Motion _originate_ from the inherent property of Motion passed by the Particles of Substance, and come from _within_, not from without. This is the best teaching of Modern Science, and also, forms an important part of the Theory of Dynamic Thought which is advanced in this book. Buchner, the author of "_Force and Matter_," vigorously insists upon this conception, saying, among many other similar expressions: "Force may be defined as a condition of activity or a motion of matter, or of the minutest particles of matter or a capacity thereof." The term "Force" is generally defined in works on Physics as "That which causes, changes or terminates Motion." The word "Force" is generally used in the sense of "in action," while "Energy" is usually used in the sense of "Potential Force--capacity for performing work," the idea being that it is "stored-up" force, or "force awaiting use." The term "Power" is used in two senses, the first meaning "a measure of Mechanical Energy," such as a "forty horse-power engine," etc.; the second sense being "Capacity or Ability to Act, or exercise Force," this use being almost identical to the idea of "Energy," as above described, although, possibly, a little stronger expression. The Materialistic school holds that Force is a property of Matter, the latter being regarded as the "real thing" of the Universe. Others hold that Force is the "real thing," and that what is called Matter, or Substance, is but a centre of Force, etc. Others hold that the two are but aspects of the same thing, calling the "thing" by the name "Matter-Force," or "Force-Matter." Haeckel calls this combined "thing" by the name of "Substance," claiming that what are called Matter and Force are but "attributes" of it, the third "attribute" being "Sensation," which he holds is akin to Mind--"Haeckel's Substance" is held to be Eternal, and Self-existent--its own Cause, in fact. (In this book the term "Substance" is not used in this sense, but merely as synonymous with what Science usually calls "Matter.")