The simplest _moral_ economy is that in which two or more interests are _reciprocally adjusted_ without being subordinated. The principle of organization which defines such an economy is _prudence_. Prudence becomes necessary at the moment when interests come into such contact with one another as provokes retaliation. Thus, for example, interests react on one another through being embodied in the same physical organism. Each bodily activity depends on the well-being of co-ordinate functions, and if its exercise be so immoderate as to injure these, it undermines itself. _Moderation_ gains for special interests the support of a general bodily health. But bodily health is not the only medium of interdependence among the interests of a single individual. His interests must draw not only upon a common source of vitality, but also upon a common stock of material resources. The limitation of interests that follows from this fact is frugality or _thrift_, the practical working of the principle that present waste is future lack, and that, therefore, to save now is to spend hereafter. Thrift involves also a special emphasis on {88} livelihood, since this is a source of supply for all particular interests. The social relation makes interests externally interdependent in a great variety of ways. Interests must inhabit one space, exploit one physical environment, and employ a common mode of communication. If any interest so acts as unduly to divert one of these mediums to its own uses, it must suffer retaliation from the other interests that likewise depend on that medium. It is prudent to give even one's rival half the road, and to divide the spoils with him. There is a politic form of _honesty_; and _veracity_ may be conceived only as a kind of caution. Thus Menander says: "It is always best to speak the truth in all circumstances. This is a precept which contributes most to safety of life." [4] _Tact_ is only a more refined method of avoiding the antagonism of interests that operate within the same field of social intercourse.