theorize on (something)
To speculate, conjecture, or form a hypothesis about something, especially in manner that is abstract or without supporting evidence. These analysts who spend so much time theorizing on the effects of these economic changes will have on the working class have no idea what it's like to actually live through them. We've theorized on several different methods of enhancing cellular regeneration, but it will be many years before technology will prove whether or not they could be viable.
theorize on something
to make a theory about something. There is no point in theorizing on something when you have all the empirical evidence you need to draw a conclusion. He spent the afternoon theorizing on the origin of the universe.