The concept of universalizability is one which was set out by the 19th century German philosopher Immanuel Kant as part of his work, the Groundwork for the Metaphysics of Morals. It is part of the first formulation of his categorical imperative, the idea that the only moral actions are ones which can be acted on as though they could rationally be willed to become a universal law, or maxim. It is possible to 'test' to determine whether a maxim is universalizable through reason, i.e. lying to suit one's own ends would fail the test, but keeping one's promises would not.