Snape paused for a moment, apparently to savour the pleasure of insulting Harry, before continuing.
“Only Muggles talk of ‘mind-reading.’ The mind is not a book, to be opened at will and examined at leisure. Thoughts are not etched on the inside of skulls, to be perused by any invader. The mind is a complex and many-layered thing, Potter—or at least, most minds are.” He smirked. “It is true, however, that those who have mastered Legilimency are able, under certain conditions, to delve into the minds of their victims and to interpret their findings correctly. The Dark Lord, for instance, almost always knows when somebody is lying to him. Only those skilled at Occlumency are able to shut down those feelings and memories that contradict the lie, and so can utter falsehoods in his presence without detection.”
Whatever Snape said, Legilimency sounded like mind-reading to Harry, and he didn’t like the sound of it at all.
“So he could know what we’re thinking right now? Sir?”
“The Dark Lord is at a considerable distance and the walls and grounds of Hogwarts are guarded by many ancient spells and charms to ensure the bodily and mental safety of those who dwell within them,” said Snape. “Time and space matter in magic, Potter. Eye contact is often essential to Legilimency.”
“Well then, why do I have to learn Occlumency?”
Snape eyed Harry, tracing his mouth with one long, thin finger as he did so.
“The usual rules do not seem to apply with you, Potter. The curse that failed to kill you seems to have forged some kind of connection between you and the Dark Lord. The evidence suggests that at times, when your mind is most relaxed and vulnerable—when you are asleep, for instance—you are sharing the Dark Lord’s thoughts and emotions. The Headmaster thinks it inadvisable for this to continue. He wishes me to teach you how to close your mind to the Dark Lord.”
Harry’s heart was pumping fast again. None of this added up.
“But why does Professor Dumbledore want to stop it?” he asked abruptly. “I don’t like it much, but it’s been useful, hasn’t it? I mean… I saw that snake attack Mr. Weasley and if I hadn’t, Professor Dumbledore wouldn’t have been able to save him, would he? Sir?”