For more than 5,000 years, "old" has been defined as beginning between the ages of 60 and 70. That means most people alive today will spend more years in elderhood than in childhood, and many will be elders for 40 years or more. Yet at the very moment that humans are living longer than ever before, we've made old age into a disease, a condition to be dreaded, denigrated, neglected, and denied. Reminiscent of Oliver Sacks, noted Harvard-trained geriatrician...