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

He is feigning ignorance about that problem.

He knows that pain through his own experience.

I have no way of knowing what he is thinking.

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

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

God only knows what he is thinking.

He starts talking about himself at every opportunity, causing trouble for the people around him.

He likes to take a walk in the park at dusk.

She described the pain of a broken heart as tears.