This picture is a good example for discussing subjectivity and objectivity. It is also a good opportunity to discuss philosophical relativism. If you were to see this object from the right side, you would claim it to be circular. If you were to see it from the left side, you would claim it to be a square.
What does solipsism, postmodernism, biocentrism, relativism –moral or any other– and supernaturalism have in common? They claim there is no “objective” reality. Invariably, a conversation about scientific realism or morality ends up hitting the wall of “subjectivity”. “But all of your arguments are only subjective! How can you say they are applicable to anyone else?” Also, invariably, quantum mechanics is used as “scientific proof” of solipsism; our “consciousness” creates the world, after all.