John Maynard Keynes:
When, on the contrary, I show, a little elaborately, as in the ensuing chapter, that to create wealth will increase the national income and that a large proportion of any increase in the national income will accrue to an Exchequer, amongst whose largest outgoings is the payment of incomes to those who are unemployed and whose receipts are a proportion of the incomes of those who are occupied...
Nor should the argument seem strange that taxation may be so high as to defeat its object, and that, given sufficient time to gather the fruits, a reduction of taxation will run a better chance than an increase of balancing the budget. For to take the opposite view today is to resemble a manufacturer who, running at a loss, decides to raise his price, and when his declining sales increase the loss, wrapping himself in the rectitude of plain arithmetic, decides that prudence requires him to raise the price still more--and who, when at last his account is balanced with nought on both sides, is still found righteously declaring that it would have been the act of a gambler to reduce the price when you were already making a loss.
Testifying before Congress in 1977, Walter Heller, President Kennedy's Chairman of the Council of Economic Advisers, summarized:
What happened to the tax cut in 1965 is difficult to pin down, but insofar as we are able to isolate it, it did seem to have a tremendously stimulative effect, a multiplied effect on the economy. It was the major factor that led to our running a $3 billion surplus by the middle of 1965 before escalation in Vietnam struck us. It was a $12 billion tax cut, which would be about $33 or $34 billion in today's terms, and within one year the revenues into the Federal Treasury were already above what they had been before the tax cut.
Did the tax cut pay for itself in increased revenues? I think the evidence is very strong that it did.
The Reagan Tax Cuts
Prior to the tax cut, the economy was choking on high inflation, high interest rates, and high unemployment. All three of these economic bellwethers dropped sharply after the tax cuts. The unemployment rate, which peaked at 9.7 percent in 1982, began a steady decline, reaching 7.0 percent by 1986 and 5.3 percent when Reagan left office in January 1989.
Inflation-adjusted revenue growth dramatically improved. Over the four years prior to 1983, federal income tax revenue declined at an average rate of 2.8 percent per year, and total government income tax revenue declined at an annual rate of 2.6 percent. Between 1983 and 1986, federal income tax revenue increased by 2.7 percent annually, and total government income tax revenue increased by 3.5 percent annually.