Dr Samuel Johnson had many illnesses, and even more ascribed to him by writers, but he had a strong constitution and lived to what was, for the time, an old age—75. He was interested in physic and was willing to experiment on himself. On his deathbed, frustrated by the inability of his doctors to relieve the gross oedema of his legs, he cut deeply into his own flesh.

Johnson, whom Voltaire (wrongly) called a superstitious dog, believed that science would help to relieve mankind of much misery, but not of misery as such. Living at a time when poverty meant not an income lower than 60% of the median …