He said that monetary policy can pretend to be close to science if it can be conducted using simple and robust rules, however, monetary policy must be closer to art if it is frequently confronted to new, poorly anticipated and poorly understood, contingencies.
In that case, each of these contingencies requires fast thinking and having to make decisions, not fully based on existing research but rather on well trained intuition. There is little doubt that monetary policy has gravitated towards being more of an art than a science. Thank you  BIS central bankers’ speeches  5