Master of history is a performer who controls and carves out social history on his own initiative.
Masses of working people are genuine masters of history. This clarifies the position occupied by the masses of working people in social history. In this sense, master of history is as same as motive force of history in meaning.
Object of history means those who are unable to carve out social history independently and creatively in accordance with their will. In other words, object of history means those who shoulder a heavy burden of making history according to the will of the exploiter class.