Open-mindedness is considered to be a virtue. But, strictly speaking, it cannot occur. A new experience must be redacted into old categories. We cannot handle each event freshly in its own right. If we did so, of what use would past experience be?

We cannot know the young child's personality by studying his systems of interest, for his attention is as yet too labile, his reactions impulsive, and interests unformed. From adolescence onward, however, the surest clue to personality is the hierarchy of interests, including the loves and loyalties of adult life.

We cannot undo the past in this misguided war in Iraq.

We cannot attribute to fortune or virtue that which is achieved without either.

We cannot embrace God's forgiveness if we are so busy clinging to past wounds and nursing old grudges.

We know there must be new physics. For example, we cannot explain what dark matter is.