The greater results of "Introspective" or, as it is very often called, "General" psychology may be summed up in a few leading principles, which sound more or less abstract and difficult, but which will have many concrete illustrations in the subsequent chapters. The facts of experience, the actual events which we find taking place in our minds, fall naturally into certain great divisions. These are very easily distinguished from one another. The first distinction is covered by the popularly recognised difference between "thought and conduct," or "knowledge and life." On the one hand, the mind is looked at as receiving, taking in, learning; and on the other hand, as acting, willing, doing this or that. Another great distinction contrasts a third mental condition, "feeling," with both of the other two. We say a man has knowledge, but little feeling, head but no heart; or that he knows and feels the right but does not live up to it. I. On the side of Reception we may first point out the avenues through which our experiences come to us: these are the senses--a great number, not simply the five special senses of which we were taught in our childhood. Besides Sight, Hearing, Taste, Smell, and Touch, we now know of certain others very definitely. There are Muscle sensations coming from the moving of our limbs, Organic sensations from the inner vital organs, Heat and Cold sensations which are no doubt distinct from each other, Pain sensations probably having their own physical apparatus, sensations from the Joints, sensations of Pressure, of Equilibrium of the body, and a host of peculiar sensational conditions which, for all we know, may be separate and distinct, or may arise from combinations of some of the others. Such, for example, are the sensations which are felt when a current of electricity is sent through the arm. All these give the mind its material to work upon; and it gets no material in the first instance from any other source. All the things we know, all our opinions, knowledges, beliefs, are absolutely dependent at the start upon this supply of material from our senses; although, as we shall see, the mind gets a long way from its first subjection to this avalanche of sensations which come constantly pouring in upon it from the external world. Yet this is the essential and capital function of Sensation: to supply the material on which the mind does the work in its subsequent thought and action.