Deontology
Etymology
From Greek "deon," meaning "that which is binding, duty," plus "logos," "study of." The English word was coined by Jeremy Bentham in the early 1800s, though for a broader sense of ethics. The systematic duty-based theory it now names is above all Immanuel Kant’s, worked out in the 1780s around his idea of the categorical imperative — act only on rules you could will everyone to follow.
noun · /dee-on-TOL-uh-jee/
The view that the morality of an action depends on whether it follows the right rules or duties, not on how it turns out.
What it names
A handle for the intuition that some things — lying, betraying, using people — are simply wrong to do, even when doing them would produce a better result.
Example
A deontologist would refuse to frame an innocent man even to prevent a riot, because the duty not to lie holds regardless of the payoff.
Related idea
Consequentialism — its main rival — judges acts purely by their outcomes. Deontology asks whether the act itself respects a duty; consequentialism asks whether the world ends up better.