For example, the inflation-overshooting commitment is more powerful than any previous forward guidance and is unprecedented; yet, at the same time it is firmly grounded in economic theories regarding inflation expectation formation developed in recent years. On the other hand, because central banks confront a constantly changing world, in practice, they often face difficulties that cannot be explained by existing theories.
When the Bank introduced large-scale JGB purchases and yield curve control, it took the limitations and issues suggested by theory into account, carefully investigated the merits and demerits of addressing those issues, and arrived at the current policy framework. I believe that such new steps in practice eventually will lead to new theoretical developments in the future.