In that connection Man is governed by natural law, a manifest law of human nature. It resembles the familiar law of external nature in obedience to which physical force advances along the line of least resistance. The former, the Economic law, may be concisely, accurately and indisputably expressed in these terms: Men seek to satisfy their Economic desires with the least exertion. The validity of that generalization is sometimes questioned on the basis of the fact that men often seek to satisfy their desires with excessive exertion. But is that true? Is it not at best only apparently true? Although for the purpose of satisfying a desire for something, one were to walk three miles when he might reach his goal and satisfy his desire by a shortcut only one mile long, but which is unknown to him or is haunted by a dreadful ghost or infested with predatory men or savage animals, or so reputed to be, he would nevertheless be seeking to satisfy his desire with the least exertion. To risk contact with a ghost or a robber or savage beasts would add much more to his exertion mental and physical, than a walk of three miles for the satisfaction of a desire that might be satisfied by a walk of one. The statement that men seek to satisfy their desires with least exertion is to be read with the interpretation that they do so with the least known and the least dreaded exertion; also that the desire may include effort for the sake of effort, for effort desired as in exercise for health’s sake or exertion for the sake of play. The Economic principle that men seek to satisfy their desires with least exertion does not imply that all men, or any of them know what the least possible exertion is. It is least only in their more or less biased or ignorant judgment. There is no contention that they do satisfy their desires with least exertion. The contention is that they naturally seek to do so. Critics of this natural law of Economics should have a care lest they fail to “see the forest for the trees.” Like the principle in physics to which it is analogous this law of Economics involves the element of least resistance. As in physics the line of least resistance may not be a straight line, although that is its tendency, so in Economics it may not be a direct line. Nor may it be the same line from generation to generation. Precisely as in physics physical obstacles may divert a line from direct to crooked, so in Economics such obstacles as customs, habits, superstitions and ignorance may cause analogous diversions. But as the physical line of least resistance, though not always the shortest by foot rule measurement, is the shortest considering obstacles, so the Economic line of least exertion is as straight as habit, custom, superstition, advice, ignorance, and other obstacles permit.