He is feigning ignorance about that problem.

In order to understand his feelings, I had a deep conversation with him.

God only knows what he is thinking.

I have no way of knowing what he is thinking.

He is working hard to make his abilities known to the world.

It's better for him not to know the truth. After all, ignorance is bliss.

My country is Japan.

My country is blessed with beautiful nature.

He is a famous author, and his works are loved by many readers.

He is an excellent doctor.