end justifies the means

actions or methods that are wrong from a moral point of view are at times necessary in order to obtain morally right results or effects

Consequentialism refers to those moral theories which hold that the consequences of a particular action form the basis for any valid moral judgment about that action. Thus, on a consequentialist account, a morally right action is an action that produces good consequences. In other words, the ends justify the means.
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(See the end justifies the means)