By increasing the number of U.S. dollars in circulation, or even by credibly threatening to do so, the U.S. government can also reduce the value of a dollar in terms of goods and services, which is equivalent to raising the prices in dollars of those goods and services.
We conclude that, under a paper-money system, a determined government can always generate higher spending and hence positive inflation. Of course, the U.S. government is not going to print money and distribute it willy-nilly (although as we 8 will see later, there are practical policies that approximate this behavior). Normally, money is injected into the economy through asset purchases by the Federal Reserve.