Short idea (6): The way humans are built we can not see the back of our heads directly, no matter what we do. We can get around this, if we want, by setting up a few mirrors or by asking others to look and tell us what they see. We also can't see the "back sides" of our own personalities. If we want to get around this we can look at our dreams (which reflect the sides of ourselves we can't see) or ask people how we look to them.