A key problem with economic policy is the persistent tendency to consider only the immediate effects of a policy, or its effects on a specially-highlighted group. It is the fallacy of overlooking secondary consequences, be they upon long term goals or other sections of society.
From this aspect, therefore, the whole of economics can be reduced to a single lesson, and that lesson can be reduced to a single sentence. The art of economics consists in looking not merely at the immediate but at the longer effects of any act or policy; it consists in tracing the consequences of that policy not merely for one group but for all groups.
Hazlitt writes rhetorically that nine-tenths of economic fallacies are because people only look at the immediate consequences of an idea, and that they only look at these consequences for a particular group.
What is of particular contemporary interest is the phrase: “There are men regarded as brilliant economists who deprecate saving and recommend squandering on a national scale as the way of economic salvation”. What was correct for Hazlitt in the 1940s is still paramount to learn today.