Whoever, in the pursuit of science, seeks after immediate practical utility may rest assured that he seeks in vain.

-Helmholtz, Hermann Ludwig Ferdinand von
  Lecture at Heidelberg, collected in Popular Lectures on Scientific Subjects (1873).

The point of equilibrium will be known by the criterion that an infinitely small amount of commodity exchanged in addition, at the same rate, will bring neither gain nor loss of utility.

-Jevons,William Stanley
The Theory of Political Economy.

Labour once spent has no influence on the future value of any article; it isgone and lost for ever. In commerce bygones are forever bygones; and we are alwaysstarting clearat each moment, judging the values of things with a view to future utility.

-Jevons,William Stanley
The Theory of Political Economy.

The creed which accepts as the foundation of morals, Utility, or the Greatest Happiness Principle, holds that actions are right in proportion as they tend to promote happiness, wrong as they tend to producethe reverse of happiness.

-Mill,John Stuart
  Utilitarianism, ch.2.

The word, it is to be observed, has two different meanings, and sometimes the utility of some particular object, and sometimes the power of purchasing other goods which the possession of that object conveys. This one may be called 'value in use'; the other,'value in exchange'. The things which have the greatest value in usehave frequently little or novalue in exchange; and on the contrary, those which have the greatest value in exchange have frequently little or no value in use. Nothing is more useful than water: but it will purchase scarce any thing; scarce any thing can be had in exchange for it. A diamond, on the contrary, has scarce any value in use; but a very great quantity of other goods may frequently be had in exchange for it.

-Smith, Adam
VALUE1776  An Inquiry into the Nature and Causes of theWealth of Nations, bk.1, ch.4.