=C. Experimental Method.=--A third method of studying mind is known as the _Experimental_ method. Here, as in the case of the ordinary physical experimenter, the psychologist seeks to control certain mental processes by isolating them and regulating their action. This may be effectively done in the study of certain processes. For instance, by passing the two points of a pair of compasses over different parts of the body, the tactile sensibility of the skin may be compared at these different parts. By this means it may be shown that the tip of the finger can detect the two points when only one twelfth of an inch apart, while on the middle of the back they may require to be two and a half inches apart to give a double impression. The experimental method is often used in connection with the objective method in Child Study. PHASES OF CONSCIOUSNESS =A. Knowledge.=--Although, as previously stated, the stream of consciousness must at all times be looked upon as a unity, it will be found upon analysis to present three more or less distinct phases. A state of consciousness implies, in the first place, being aware of something as an object of attention. In other words, something is seized upon by consciousness as a presentation, and to the extent to which one is aware of this object of consciousness, he is said to recognize, or to know it. A state of consciousness is always, therefore, a state of knowledge, or of intelligence. Thus, whether we perceive this chair, imagine a mermaid, recall the looks of an absent friend, experience the toothache, judge the weight of this book, or become angry, our conscious state is a state of _knowledge_. =B. Feeling.=--A conscious state is also a state of feeling. Every conscious state has its feeling side, since it is a personal state, or since the mind itself is affected toward its own state. Two men, for instance, may know equally well the taste of a particular food, but the taste may affect each one quite differently. To one the experience is pleasant, to the other it may be even painful. Two boys may know equally that a point has been scored by the visiting team, but the personal attitude of each toward the experience may be quite different. The one finds in it a quality of joy; the other a quality of sorrow. In the same way the mind always feels more or less pleased or displeased in its present state of consciousness. To speak of any particular experience as painful, joyous, sorrowful, etc., is, therefore, to refer to it as a state of _feeling_.