Only through the medium of the public physical world can the mind of one person make a difference to the mind of another. The mind is in its own place and in each of us lies an inner life, the life of a ghostly Robinson Crusoe. People can see, hear, and jolt one another's bodies, but they are irremediably blind and deaf to the workings of one another's minds
Quack: A boastful pretender to arts which he does not understand. A vain boastful pretender to physick; An artful, tricking practitioner in physick.