Consideration of the characteristics of the field of action may thus disclose features which will greatly influence the possibility of accomplishment, as well as the character of the effort to be made, from the standpoint of feasibility. The second requirement, therefore, is that of feasibility with respect to comparative resources, i.e., the means available and opposed, as influenced by the physical conditions prevailing in the field of action. Although believed to be both suitable and feasible, the requirements for the attainment of an end are not yet completely established. There is still required a reckoning of a profit-and-loss account of the whole undertaking, to estimate whether it will be advantageous. What will be the cost, and what will be the gain? Is the effort worth while? Or should one be content with venturing less and gaining less? What is the bearing on possible future action? The consequences as to costs, always important considerations in dealing with human problems, are frequently the paramount determinant. The third requirement, therefore, is acceptability with respect to the consequences as to costs. These requirements invite attention to the factors, already discussed, whose influence (see page 25 as to factors) determines the character of the effort required to attain an end. The Fundamental Principle for the Attainment of an End. Here, then, are the broad fundamental considerations which affect the solution of every human problem. In a narrower field, the considerations may fall within more specific limits, but a principle sufficiently broad to be applicable to all cases appears to comprehend those inclusive factors mentioned in the preceding paragraphs. A review of these paragraphs will disclose that the factors pertaining to the several requirements may be so grouped as to constitute a single fundamental principle governing the attainment of an end in human affairs,--as follows: In any human activity, the attainment of a correct end in view depends on fulfillment of the requirements of Suitability of the end in view, as determined by the factor of the appropriate effect desired, Feasibility of the effort required, on the basis of comparative resources, as determined by the means available and opposed, influenced by the factor of the physical conditions prevailing in the field of action, and Acceptability of the results of the effort involved, as determined by the factor of the consequences as to costs, which factors are in turn dependent on each other. The Interdependency of the Factors. As previously observed (page 28), the factors cited in the foregoing principle are themselves interdependent. This fact results from working of natural law (page 22), for it is a recognized phenomenon that every effect is the result of certain causes, and that every effect is itself, in turn, the cause of further effects (page 19).