There are many types of deontological moral philosophy, all having in common the assumption that duty, obligation, tightness-wrongness, and related concepts, are primary in ethics. The empirical value of consequences, the "good life," and so on, are ancillary.
It will prove fruitful however to draw a distinction between two types of deontological theory. The one type I shall call (following James on determinism) hard deontologism, and the other soft deontologism. The best known hard deontologists are the strict Judaic-Christian moral philosophers and Immanuel Kant. I would consider W.D. Ross to be a classical soft deontologist. His notion of prima facie duties, presented in hierarchical order, surely suggests a markedly softer approach to the choice of one's obligations, even though a prima facie duty has intrinsic value.
An obvious example of a hard deontological decision would be Abraham's unquestioning obedience to God's demand that Issac, Abraham's only son, be sacrificed at the altar. God's word, as the source of all obligation, takes precedence over anything else, even though requiting a hideous action having heartrending consequences.
And consider Kant's well-known reply to the French philosopher who asked him whether he would not lie if confronted at his front door by a madman with a firearm looking for one of his, Kant's, close friends, who happens to be dining in the next room. Kant answered that there is still the alternative of remaining silent. This is genuine hard deontologism!
The soft deontologist, on the other hand, like the soft determinist, wants, I think, to have his cake and eat it too. What else can be the import of Ross's prima facie duties? We have some kind of insight into what is absolutely binding upon our moral conduct. And yet we must hedge this insight by taking into account first appearances and evaluations of degrees of obligation.
In general any deontologist maintains that the obligation to obey certain moral rules does not rest on the consequences of an act. Rather one is