It was just like some ancient electricity-powered computer; it didn't matter how fast, error-free, and tireless it was, it didn't matter how great a … - Iain Banks

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It was just like some ancient electricity-powered computer; it didn't matter how fast, error-free, and tireless it was, it didn't matter how great a labor-saving boon it was, it didn't matter what it could do or how many different ways it could amaze; if you pulled its plug out, or just hit the off button, all it became was a lump of matter; all its programs became just settings, dead instructions, and all its computations vanished as quickly as they'd moved.
It was, also, like the dependency of the human-basic brain on the human-basic body; no matter how intelligent, perceptive and gifted you were, no matter how entirely you lived for the ascetic rewards of the intellect and eschewed the material world and the ignobility of the flesh, if your heart just gave out...
That was the Dependency Principle; that you could never forget where your off switches were located, even if it was somewhere tiresome.