Pessimism is when you think negative and optimism is vice-versa, so what do you call it when a person determines an outcome to be either as opposed to assuming which way it will be?
You mean like being a realist?
There is no reality, only perception. How ever you see a situation is what it is to you. Not everyone will see it the same. A situation that is positive to you may be negative for others.
[not influenced by personal feelings, interpretations, or prejudice; based on facts; unbiased: an objective opinion.]