The Metaphysics of Morals by Immanuel Kant Chapter 1 Page 30

promise) should hold good as a universal law, for myself as well as for others?” and should I be able to say to myself, “Every one may make a deceitful promise when he finds himself in a difficulty from which he cannot otherwise extricate himself?” Then I presently become aware that while I can will the lie, I can by no means will that lying should be a universal law.

For with such a law there would be no promises at all, since it would be in vain to allege my intention in regard to my future actions to those who would not believe this allegation, or if they over hastily did so would pay me back in my own coin. Hence my maxim, as soon as it should be made a universal law, would necessarily destroy itself.

I do not, therefore, need any far-reaching penetration to