What makes this observation worth your attention is that Einstein isn't merely celebrating intellectual curiosity—he's describing an irreversible neurological fact. Once you've genuinely understood someone else's way of seeing the world, you cannot unknow it; the very architecture of your thinking has shifted. Consider how learning that your closest friend holds a political belief opposite yours doesn't just add information—it forces you to hold two competing truths simultaneously, and that cognitive stretching alters you permanently. The quote matters because it explains why well-read people often seem restless: they've become too large for any single perspective to contain them.