Formation of the experimental method—The intervention of religion in disease—Disease as a basis of pessimistic systems of philosophy—Advance of medical science in the war against disease—The revolution in medicine and surgery due to the discoveries of Pasteur—The beneficial results of Serum Therapy in the war against infectious diseases—Failure of science to cure tuberculosis and malignant tumours—Protests against the advance of science—Opposition of Rousseau, Tolstoi, and Brunetière—Proclamation of the fallibility of science—Return to religion and mysticism Science, the youngest daughter of knowledge, has begun to investigate the great problems affecting humanity. The chief religions and many systems of philosophy had been long established before the spirit of scepticism dared to inquire whether or no these products of the human mind were really in harmony with fact. Scepticism gained ground little by little, and open war was declared between religious dogma and authority on the one side, and scientific reason on the other. The great religions and the philosophy of Aristotle had ruled a majority of mankind for some twenty centuries before doubt was cast on the real value of these doctrines. Francis Bacon, Lord Verulam, asked why it was that all the systems of his time were so vague and so powerless to explain the phenomena of the world. The cause could not lie in nature herself, for without doubt she followed laws that were immutable and that could be subjected to exact observation; nor could it lie in any want of intelligence in those men who devoted themselves to solve the problems. The true cause of the failure lay in the falsity or insufficiency of the methods employed. Bacon, trying to provide a remedy for this condition of affairs, advised that makers of generalisations should proceed very slowly, passing only by the smallest stages from particular facts to conclusions only more general in the slightest degree, and so on, until the ultimate formula might be reached. By such a path it was possible to attain principles neither vague nor ambiguous, but clear and exact and that would not be denied by nature herself.