a necessary evil
- something unpleasant that must be done in order to achieve a goal or objective
- something displeasing that must be accepted just to achieve a desired result
- anything bad that has to be carried out or condoned in order to achieve something good
- Mike saw his going to work for his father as a necessary evil if he was ever to own his own company someday
- Getting a good education is seen by some as a necessary evil to get a chance at a better life.
- David's marriage to Ann is simply a necessary evil.
- No matter the lawyer's strong case of self-defence, the judge just couldn't see the murder as a necessary evil.
- In as much as stealing is a crime, sometimes, people have no other means to survive and this can make it a necessary evil.
This phrase goes back to the ancient Greek times. The first usage of the phrase "necessary evil" was with reference to Marriage. The act of marriage was seen as a necessary evil because it was really expensive and cumbersome, yet it was the only legal way towards procreation. After this reference to marriage as a necessary evil, the phrase gradually became popular in everyday use.