More detail from his speech:
I think it is quite possible that the conditions the Committee has established to begin to normalize monetary policy could soon be satisfied. In particular, I will be evaluating the incoming information to see if it confirms my expectation that growth will be sufficient to further tighten the U.S. labor market.
After lift-off commences, I expect that the pace of tightening will be quite gradual. In part, that is because monetary policy is not as stimulative as the low level of the federal funds rate might suggest. There is strong evidence that the short-term neutral real interest rate—let’s call that r*—is currently quite low, certainly below the level that historically has applied on a longer-term basis...
I see the risks right now of moving too quickly versus moving too slowly as nearly balanced. The weight that one puts on each undoubtedly influences one’s views on when the time will be right to begin to normalize monetary policy and the appropriate short-term rate trajectory thereafter.The full speech is here.