Is there a single best move in every position? If it were possible to analyse every possible outcome of a position, would there ever be a single move that could be considered "best"?

I know that this is how computers evaluate positions, but they can only calculate the decision tree down to a set number of moves. If it were possible to analyse every possible outcome in a reasonable amount of time (possibly with quantum computing), could the ultimate chess move be made?

What I guess I'm saying is that is a chess move objective in that only one move is really the best one, or should it be subjective in that it makes certain assumptions about the opponent? For example a move may be made that 90% of players are not "good enough" to counter, and therefore that move was a good move (what I mean by subjective). However, there may be another move that is more strategic which increases the chances of victory against 100% of players, but this would not be known to anyone unless it was possible to make an exhaustive analysis of every single outcome (objective).
No, there are positions in which a lot of moves have the same effect or are the same but you can play them in a different order.