In ordinary experience everybody estimates value by some comparison with what he can obtain in exchange. A picture of a friend may be priceless in two senses: first, of so great importance to its owner that nothing can buy it; second, of so little importance to anybody else that nobody will give anything for it. In any inventory of wealth the picture could not be counted; it is valueless. But in any judgment of personal welfare it may be beyond price. So, in the universal experience, the term value has come to be used as essentially connected with exchanges and with property as stored to meet all kinds of wants. _Value in services._—In a similar way experience has developed the idea of value with reference to services. A service may be invaluable, as when a physician saves the life of his patient, but the value of that service is estimated by the return expected in the community where the physician and his patient live. Many services of highest usefulness and most important in welfare cannot be valued in terms of wealth, because no wealth can secure them. Love and patriotism and philanthropy cannot be had for wealth. But in comparison of two services rendered for hire, both are measured by their general utility, either directly or indirectly, and even this estimate is modified by the readiness with which either service can be secured. One who seeks the service of an artist who stands alone among ten thousand people, may be willing to give the services of a thousand other men, which can be had for a trifle, because they are everywhere abounding. _Essentials of value._—Experience seems, therefore, to settle upon three conditions for value in any article of wealth or any service rendered. First, the article or service must have utility—that is, it must be useful in satisfying somebody’s wants, either present or future. Second, those wants must be of such a nature that effort on the part of some human being will be necessary to gratify them. Nothing which can be had at all times by mere desire of it can have value. Third, the object must be of such a nature as to command other services or exchange of other wealth. For this reason it must be transferable from one owner to another. _Utility as related to value._—While utility is a basis of all values, it is not the chief element in measuring the value of wealth. The things of highest utility, like air and water, have no value as long as trifling exertion will bring them. Even land is without appreciable value so long as any person can obtain it by settling upon it.