A huge amount of our everyday thinking - powerful, creative, and resonant stuff - is done socially: talking to other people, arguing with them, relying on them to recall information for us.
We use paper documents to store knowledge so we can consult and reconsult it, giving us a type of recall impossible with our unaided minds; we use pencils to scratch down material so we can manipulate it in a fashion impossible in our unaided minds.