We cannot here go into the proof of the doctrine of development. For this proof, the reader must be referred to zoölogy. One further point, however, may be noted. If it is difficult for the reader to conceive of the development of mind on the earth similar to the development of animals in the past, let him think of the development of mind in the individual. There can certainly be no doubt of the development of mind in an individual human being. The infant, when born, shows little manifestation of mentality; but as its body grows, its mind develops, becoming more and more complex as the individual grows to maturity. =The World as Dynamic.= The view of the world outlined above, and held by all scientific men of the present time, may be termed the _dynamic_ view. Man formerly looked upon the world as static, a world where everything was fixed and final. Each thing existed in itself and for itself, and in large measure independent of all other things. We now look upon things and events as related and dependent. Each thing is dependent upon others, related to others. Man not only _lives in_ such a world, but is _part of_ such a world. In this world of constant and ceaseless change, man is most sensitive and responsive. Everything may affect him. To all of the constant changes about him he must adjust himself. He has been produced by this world, and to live in it he must meet its every condition and change. We must, then, look upon human nature as something coming out of the past and as being influenced every moment by the things and forces of the present. Man is not an independent being, unaffected by everything that happens; on the contrary, he is affected by all influences that act upon him. Among these influences may be mentioned weather, climate, food, and social forces. The condition of the various organs of a child's body determine, to some extent, the effect which these various forces have upon it. If a child's eyes are in any way defective, making vision poor, this tremendously influences his life. Not only is such a child unable to see the world as it really is, but the eyestrain resulting from poor vision has serious effects on the child, producing all sorts of disorders. If a child cannot hear well or is entirely deaf, many serious consequences follow. In fact, every condition or characteristic of a child that is in any way abnormal may lead on to other conditions and characteristics, often of a serious nature. The growth of adenoids, for example, may lead to a serious impairment of the mind. Poor vision may affect the whole life and character of the individual. The influence of a parent, teacher, or friend may determine the interest of a child and affect his whole life. The correct view of child life is that the child is affected, in greater or less degree, by every influence which acts upon him.