Though the utilitarian movement only came into its own in the nineteenth century with the philosophy of John Stuart Mill, the philosophy of an earlier utilitarian philosopher, Jeremy Bentham was already published in Kant's lifetime. In his work "an Introduction to the Principles of Morals and Legislation," Bentham held that the role of philosophy, and of ethical action, was to determine the greatest good, or "utility," for the greatest number.
Utilitarianism would become a central moral defense of the Industrial Revolution and the rise of capitalism. Because it can point to actual human happiness as its result, students tend to respond more warmly to it. The power of Kant's moral philosophy is in demonstrating just how shaky many of the seemingly "concrete" bases we have for morality, including demonstrable human happiness, are. What if we had the choice between bringing permanent, calm happiness to ten people at the cost of bringing extreme, unbearable unhappiness to one person? Kant would consider such considerations, together with the numerical, quantitative estimation of happiness, to be an absurdity, beneath the dignity of human beings. Kant's philosophy, icy though it might seem, is based on the idea that happiness is a task for human beings, something towards which we strive, and something that only has real meaning if it is achieved on a durable basis by the inner harmony of the individual with his rational faculties. Kant offers a much deeper understanding of happiness: happiness is when we feel pleasure because we have done our duty, thereby bringing together our rational and sensual sides.
