theorize about (someone or something)
To speculate, conjecture, or make guesses about someone or something. Everyone has been theorizing about what the company's next product might be. If I'm going into business with someone, I don't want to have to speculate about them, their past, or their motivations—I want concrete facts.
theorize about someone or something
to hypothesize about someone or something; to conjecture about someone or something. Let's not waste time theorizing about Ted. He won't change. I can only theorize about what happened.