In the economic sphere an act, a habit, an institution, a law produces not only one effect, but a series of effects. Of these effects, the first alone is immediate; it appears simultaneously with its cause; it is seen. The other effects emerge only subsequently; they are not seen; we are fortunate if we foresee them.
There is only one difference between a bad economist and a good one: the bad economist confines himself to the visible effect; the good economist takes into account both the effect that can be seen and those effects that must be foreseen.
Yet this difference is tremendous; for it almost always happens that when the immediate consequence is favorable, the later consequences are disastrous, and vice versa. Whence it follows that the bad economist pursues a small present good that will be followed by a great evil to come, while the good economist pursues a great good to come, at the risk of a small present evil.
The essay has a number of subsections: the Broken Window; the Disbanding of Troops; Taxes; Theatres, Fine Arts; Public Works; the Intermediates; Restrictions; Machinery; Credit; Algeria; Frugality and Luxury; and He Who Has a Right to Work Has a Right to Profit.
I'm not an economist, but this sounds like good argument as to why many government economic measures don't work, particularly public works spending and tariffs.
I found the essay very interesting and worth the time it took to read. I'd be interested in looking at articles debunking Bastiat's thoughts.