In its strongest form, rationalism claims that all knowledge is derived from the workings of our minds. In this strong form rationalism asserts that the universe is in fact our opinion. We think there are rocks and trees and oceans and so there are. For most people, empiricism makes more sense than rationalism - at least in their strong forms. It takes a bit of effort to see knowledge in rationalist terms, but it can be done.
Artists do it.
Georgia O'Keefe, for one, described in some detail the process she went through in attempting to think of the world in a unique way and then to paint that world as she saw it - as it existed in her mind. Objective painting is not good painting unless it is good in the abstract sense. A hill or a tree cannot make a good painting just because it is a hill or a tree. It is lines and colors put together so that they say something. For me that is the very basis of painting.