The opening words of Nicodemus, “We know” are an indication that he has come with preconceived notions and not with openness. It also indicates that he is of the opinion that he does not need to learn anything. This is a dangerous attitude for one to have. Learning never ends. We need to realize this and, with this realization, must come an openness and desire to learn.
His closed attitude also prompts him to set limits on what God can and cannot do and his “we know’ soon takes the form of “How can”? He is unwillingly to let God be God. His categories are all well defined and no amount of explanation will break through them. Sadly, he starts with “We know" and ends with "How can?" and so learns nothing.