Our hero did not answer, but he was doing some hard thinking.

"We both need to cool down and do some hard thinking."

"I've been doing some hard thinking lately about what I want to do with the rest of my life."

The question is still in debate after more than a decade of hard thinking.

I'm going to stay down here and do some hard thinking.

Often, in a tight situation, his mind would seem to grow tired from so much hard thinking.

It just needs hard thinking and a bit of fire in the belly.

And now we need to do some very hard thinking, young man.

My guess is that they are creatures who have had time enough to do a little hard thinking.

I just need to go home and do some hard thinking.