"The Common Good"

"Common" in this case means "collective", rather than "ordinary". Its meaning is closer to "communist" or "everyone" than to the more "common" meaning. "General welfare" is another way to say the exact same thing.

What is "good"? Good is something that actively helps or benefits someone who is not harming others. It isn't just an absence of "evil" since there are neutral acts that are neither "good" nor "evil", such as walking across the room. (It is never "good" to help harm innocent people. This is an excellent reason to refuse to help the police. Ever.)

So, "the common good" (or "general welfare") would be something that helps "everyone".

The only way to help "everyone" is to help the individual. Yet, most of the time "the common good" is invoked as an excuse to harm the individual. When that individual is not deserving harm right now, then the act of harming him is evil. Violating the rights of an individual; taking away the freedom of an individual, except as an act of individual self-defense, is not serving "the common good" in any way. It only serves the state and other parasites. Instead of imagining you are helping the majority, you need to think about the minority you are harming. That is the true measure of the "good" of your acts. It is better to do nothing (and therefore not help some people) than to do something which harms some who do not deserve to be harmed right now.