The second formula of the categorical imperative says to treat all humanity, whether it is one's own self or any other human being, always as an end-in-itself and never as a means only (p.36; 429). If advancing one's own ends could possibly prevent the ends of another person or if that other was manipulated or coerced in any way to doing or not doing an action, then the action fails the second formula. This principle is the underlying reason to adhere to the maxim about lying. Lying is a way of manipulating the information that one allows others to know, which is essentially for selfish reasons. Therefore the liar is advancing his or her own ends while failing to treat the person being lied to as an end-in-itself. .
Lying, or making a false promise, is a self-contradiction in the sense that when one says that he or she will do one thing but they really mean or do the opposite; the lie is ultimately for selfish reasons. If lying is accepted as a morally permissible action, then we would not be able to tell when someone is telling the truth nor could we trust the word of anyone to do a morally right action. Setting a principle that prohibits lying of any kind for any situation is universalizable because we would want others to follow the same example given the same or even different circumstances (p.30; 421); it also helps to enable a moral system that contains selfless motives. However, while non-contradiction is held in high esteem when it comes to moral matters, the most important matter is the value of human life. What if the maxim that pertains to lying could conceivably be broken so that there could be a morally permissible, and selflessly motivated, reason to lie to someone?.
Imagine a situation in which moral agent A had to decide to either tell the truth or to consciously lie, however telling a lie could possibly prevent another person from physical harm, a selfless motive, and telling the truth could certainly bring someone in direct physical harm.
