  We show that human mental states are unresolvable by suggesting a
mathematical function that describes human mental states in relation to
parallel universe theory. The function is a solution to a multi-dimensional
advection equation; representing a situation a person is faced with, and its
time-derivative showing the mental state in that situation. This function has
interesting characteristics that explain why each person has different thoughts
in a particular situation. Because the multi-dimensional advection equation has
an infinite number of solutions, we can use them to represent an infinite
number of mental states. We focus on the basic concepts of the model and
explain the function using extremely simple cases. We also use the functions to
explain remembering and forgetting.
