Deontology focuses on people’s reasons for acting in considering whether a particular action is right or wrong. Specifically, what one should do in any given situation is the action that is based on the best reasons. Immanuel Kant proposed a very famous deontological position, and so we will focus on his views here.
Kant held that one could do something that resulted in good things but that was motivated by bad reasons. When this happens, the person has still done something wrong. So, imagine a person who decides not to be a criminal because he is scared of going to jail. For Kant, even though this person ends up doing a good thing, his reasons are bad, and so he has done something immoral. The person should have opted not to be a criminal because he should have acted for the sake of duty and out of a responsibility to respect others.
Kant held that above all, there was one ultimate reason on which we should always act; he called this the categorical imperative—meaning that it is the imperative of morality (“be moral!”) that applies categorically (i.e., to all of us, all the time). His most famous, but complicated and slippery, formulation of the categorical imperative was to “act so that the maxim of your action can be willed as a universal law.” This is very close to saying “don’t make an exception for yourself,” or “do unto others as you would have them do unto you.” Kant claims this is equivalent to saying that you should always respect others, and “always treat them as an end to themselves, never as a mere means.” This second formulation, thankfully, is a lot easier to use. Doing the right thing means respecting others, not using them—even for good ends, and even “for their own good.”
For Kant, the duty to respect others is absolute, and it’s never right to fail to respect others for the greater good. He put this bitter pill to the test by considering an extreme case: He asked us to imagine that a friend had sought shelter in our home from someone who intended to do violence to him. In this case, Kant says, if this angry man comes to our door looking for our friend, it is still wrong to lie and say we don’t know where he is. This is often, but misleadingly, called “the murderer at the door example.” This is a misleading name for the example because it assumes that this angry stranger is a murderer, and that’s exactly the kind of disrespect that Kant says is wrong. So long as we treat this man as a murderer and lie to him to protect our friend, we deny the stranger the opportunity to do the right thing. By lying to him, we fail to respect him as a moral agent, and we use him as a means to protect our friend, robbing him of the opportunity to choose the right thing and to redeem himself and become righteous. This doesn’t mean we need to simply hand over our friend, though—we can argue with the angry stranger; we can call the police; we can put our own life on the line by protecting our friend from harm. But deceit is always immoral: We owe everybody respect, and two wrongs don’t make a right.
It’s a view that may seem harsh and uncompromising, but it can be very helpful in keeping us away from making excuses for ourselves and wrongly justifying being unfair to others.