How merciful a thing is man's ignorance of his immediate future! What a ghastly, paralysing thing it would have been if all those present could have known what was about to happen within a matter of seconds! For nothing short of pre-knowledge could have stopped the occurrence, so suddenly it sprang upon them.
Mental ghettos are not mirages; they actually exist in palpable reality: being "open" inside one's mental or intellectual ghetto does not open its door but simply allows one to harbour the illusion that there is no ghetto and no door. The most dangerous prisons are those with invisible bars.
Do you mean ter tell me," he growled at the Dursleys, "that this boy - this boy! - knows nothin' abou' - about ANYTHING?"
Harry thought this was going a bit far. He had been to school, after all, and his marks weren't bad.
"I know some things," he said. "I can, you know, do math and stuff.