We are face to face with this great world, and our relations to it are manifold. One of these is the necessity we have to live, to till the soil, to gather food, to clothe ourselves, to get materials from nature. We are always making things that will satisfy our needs, and we come in touch with nature in our efforts to meet these needs. Thus, we are always in touch with this great world through hunger and thirst and all our physical needs. Then, we have our mind; and our mind seeks its own food. The mind has its necessity also. It must find out reason in things. It is faced with a multiplicity of facts, and it is bewildered when it cannot find one unifying principle which simplifies the heterogeneity of things. Man's constitution is such that he must not only find facts, but also some laws which will lighten the burden of mere number and quantity.