Re: Star Trek morality test - best and worst episodes
^ It's the key difference between the TOS PD and the TNG PD: The TOS Prime Directive was concerned with avoiding harm to aliens and alien cultures. The TNG version is concerned with protecting some vacuous "cosmic plan," even if that means allowing aliens and their cultures to be harmed to the point of extinction. Basically, it's a "get out of jail free card" for cowardice and inaction.
"There are two means of refuge from the miseries of life: music and cats." - Albert Schweitzer