The graph below shows two possible AD lines. Notice that as AD moves to the right, the price level (and therefore the inlfation rate) will increrase faster and faster. So we need to be careful not to let AD move past QF, which is called the full-employment GDP or level of output. But right now Fed officials disagree as to how close AD is to this point. The closer it is, the more careful we have to be in increasing the money supply.
A Wall Street Journal Article, Fed Vice Chairman Sees Tamed Inflation Threat. Here are the conflicting statements:
""I expect the persistence of economic slack, accompanied by stable longer-term inflation expectations, will keep inflation subdued for some time," Mr. Kohn said. "The substantial rise in the unemployment rate and the plunge in capacity utilization suggest that the margin of slack in labor and product markets is considerable. Long-term inflation expectations remain stable, and inflation itself could move "appreciably lower" should expectations decline, Mr. Kohn noted."
"His views contrast with those of others, including St. Louis Federal Reserve Bank President James Bullard, who this week warned that the existence of "slack" could be exaggerated, posing potential inflation problems in the medium term."
In the graph below, I have two AD lines, on representing the comments of each economist. The one for Kohn has alot more room to move to the right without increasing prices or inflation very much. If he is right, then there is alot more the Fed can do to help the economy recover. But if Bullard is right, and if the Fed tries to add money and AD to the economy, prices will rise very quickly because the SRAS line starts getting very steep past QF.