A common way to classify duties has been to distinguish between positive (duties that prescribe certain actions) and negative (duties that proscribe actions). “Don't kill” is an example of a negative duty, while “Do right by others” is an example of a positive one. Negative duties, which must be observed absolutely, have often been called “strict,” while their counterparts are called “broad.” The prohibition against killing is absolute and therefore a strict duty, whereas one has a bit more latitude when it comes to positive duties. There are many ways of being charitable, for example, and one can be devoted to a greater or lesser extent.

There's some justification for this distinction, but its importance shouldn't be exaggerated. Clearly, some duties are positive and others negative; but no duty is less obligatory than any other, despite what popular sayings tell us. According to one such saying, “Justice is our most fundamental duty, and anyone who wishes to remain within the bounds of humanity must be faithful to it. Charity, by contrast, is a luxury we're not obliged to give.” Another saying holds that “in rendering to each that which is his due, we do only what we must. If we go beyond this, we deserve special credit, because charity is less required of us than are other duties.” On this view, negative duties are more obligatory, whereas positive duties are more meritorious.

Although many people think otherwise, positive duties are as obligatory as any.