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.

He practices every day to learn new skills.

By participating in that project, he was able to give some dignity to his career.

I was surprised by his ill-bred attitude.

I can't stand his impudent attitude.