The scientist first gathers together the greatest possible array of experiential facts and classifies these facts into sequences--that is to say, he gathers together as many instances as he can find in which one given fact follows directly upon the happening of another given fact. Having done this, he next formulates in broad general terms the common principle that he finds embodied in these many similar sequences. Such a formula, if there are facts enough to establish it, is what is known as a scientific law. Its value to the world lies in this, that whenever the given fact shall again occur our knowledge of the scientific law will enable us to predict with certainty just what events will follow the occurrence of that fact. First, then, let us marshal our facts tending to prove that bodily activities are caused by the mind. INTROSPECTIVE EVIDENCE OF MENTAL MASTERY CHAPTER IV INTROSPECTIVE EVIDENCE OF MENTAL MASTERY [Sidenote: Doing the Thing You Want to Do] The first and most conspicuous evidential fact is voluntary bodily action; that is to say, bodily action resulting from the exercise of the conscious will. [Sidenote: Source of Power of Will] If you will a bodily movement and that movement immediately follows, you are certainly justified in concluding that your mind has caused the bodily movement. Every conscious, voluntary movement that you make, and you are making thousands of them every hour, is a distinct example of mind activity causing bodily action. In fact, the very will to make any bodily movement is itself nothing more nor less than a mental state. _The will to do a thing is simply the belief, the conviction, that the appropriate bodily movement is about to occur._ The whole scientific world is agreed on this. For example, in order to bend your forefinger do you first think it over, then deliberately put forth some special form of energy? Not at all: The very thought of bending the finger, if unhindered by conflicting ideas, is enough to bend it. [Sidenote: Impellent Energy of Thought] Note this general law: _The idea of any bodily action tends to produce the action._ This conception of thought as impellent--that is to say, as impelling bodily activity--is of absolutely fundamental importance. The following simple experiments will illustrate its working. Ask a number of persons to think successively of the letters "B," "O," and "Q." They are not to pronounce the letters, but simply to think hard about the sound of each letter. [Sidenote: Bodily effects of Mental States] Now, as they think of these letters, one after the other, watch closely and you will see their lips move in readiness to pronounce them. There may be some whose lip-movements you will be unable to detect. If so, it will be because your eye is not quick enough or keen enough to follow them in every case.