A view on motives (Kelsey Hunter, Week 2 Dialog)

After reading Morgenthau's piece and discussing it as a small group in class, we found ourselves stuck on Morgenthau's rejection of motives as playing a role in politics. He says if we had access to the motives of statesmen, which in reality it is impossible to know the motives of even ourselves, those motives would not predict the foreign policy decisions of that statesman. Morgenthau discards motives because they don't indicate any clues as to the actions taken by the state.
I am of the belief that motives don't matter primarily because if Realism is concerned with history, results are what matter the most. It doesn't matter what a statesman's motives are if he does not take actions that achieve those motives. So if Statesmen A is motivated by a hunger for power, if he does not gain power through his actions we will never know that his motive was to gain power. Power is a legitimate motive in politics, but if the results are not an increase in power it does not matter that the motive was power. If we look back in history, the reason we shouldn't concern ourselves with motives is because motives do not always guarantee results. The reason Morgenthau says Realists ignore motives is because they don't predict anything and Realism is trying to explain the world and the actions of states in a rational and logical manner. Motives are unpredictable and contain various psychological and philosophical tints, and if the motive does not match the outcome of the actions taken, we can never pretend to know what those motives were in the first place.