In addition to the endless pleadings of self-interest, there is a second main factor that spawns new economic fallacies every day. This is the persistent tendency of men to see only the immediate effects of a given policy, or its effects only on a special group, and to neglect to inquire what the long-run effects of that policy will be not only on that special group but on all groups. …
In this lies almost the whole difference between good economics and bad. The bad economist sees only what immediately strikes the eye; the good economist also looks beyond. … The bad economist sees only what the effects of a given policy has been or will be on one particular group; the good economist inquires also what the effect of the policy will be on all groups.

Henry Hazlitt (1946). Economics in One Lesson, p 3-4