It is, of course, not to be forgotten that every time we use a word, whether we read it, speak it, or hear it, the meaning it arouses is traceable to the fact that firm bonds have been established between the eye, ear, and throat mechanisms on the one hand, and related parts of the body which are involved on the other. This union of the reading-reflexes with the somatic-reflexes is provided for by a very simple mechanism called the conditioned reflex. By such a device, any two reflexes which have been aroused _together_ frequently enough by external stimuli will ever thereafter tend to arouse each other. That is why the word “fire” which we all were taught to use to indicate a certain kind of object, will, even if spoken in a wilderness of snow, make us feel some of the effects which flame once produced upon us. Contrariwise, the blindfolded man will, by no other cue than the touch of his fingers, name such objects as carpet, leather, sandpaper, and nails. And from what we have already said about the source of the meaning of abstract terms being traceable to concrete experiences, we may now say that such words as cheap, beautiful, and good, one and all owe their significance to the fact that they too exhibit the law of the conditioned reflex both in their origin and in their maturity. _How the “All-or-none” Principle Helps to Disclose an Amazing Secret_ It being thus apparent that words possess meaning because they arouse motor tendencies in us, let us now see what justification there is for the assertion previously made that these motor tendencies need not be at all visible as overt actions in order to perform their epistemological function. This justification is found in the all-or-none principle of nervous and muscular activity,—a principle having the most far-reaching consequences for both psychology and ethics. We are all familiar with the fact that less work is involved in lifting the arm leisurely to a horizontal position than in moving it through the same radius with a heavy weight held in the hand. However, we are not all familiar with the fact that in the case of the leisurely movement only a few of the myriad nerve and muscle fibers of the arm are being innervated, the rest being completely passive, while in the case of lifting the heavy weight, the proportion of fully active and inertly passive fibers is just the opposite. But this is exactly the case. According to the all-or-none principle discovered by Lucas and Adrian,[3] whenever a single nerve fiber functions at all, it acts in its maximum capacity. Never is such a fiber partially activated; in its all-or-none functioning it is as uncompromising as gravity. Consequently, even though the arm may _feel_ uniformly flabby when it is indolently moved about, some few of its nerve and muscle fibers are working to their limit.