We know the hard way: there are certain thoughts an intelligent mind must not think.

He felt that strange feeling again, of his mind wanting to think certain thoughts without having the right words.

"We all have mental privacy, but certain thoughts are more accessible."

He'd been trying to suppress certain thoughts, but not very successfully.

That is not the point, said Leader, its thoughts hard and certain.

My only children are certain thoughts I may have been able to give you.

A certain thought was swelling in my head, growing until I couldn't ignore it any longer.

You can put certain thoughts out of your mind.

"Often, you think you're the only one out there with certain thoughts and experiences."

Jill shook her head as if to drive certain thoughts out of it.