The Greek conception of a life in harmony with nature found its most complete development in the rationalism of the Renaissance, and of the centuries that followed it. Hutcheson,[10] a Scotch philosopher of the eighteenth century, insisted that right was with the thinkers of the naturalistic school, and that the realisation of their ideal was to be considered as the highest virtue. He thus placed himself directly against the Scotch clergy who asserted the greatest contempt for human nature. Buckle[11] proclaimed that it was a high honour for Hutcheson to have been the first Scotchman to raise his voice publicly against the degrading views of his time. The French philosophers of the eighteenth century, who sought to replace the religious foundations of conduct by rational principles, again had recourse to human nature. Not long before the French Revolution there appeared a treatise in three volumes, written by Baron d’Holbach, and entitled, “Universal Morality, or the Duties of Man based on Nature.”[12] Frankly a materialist and atheist, that writer laid it down as an axiom that “to be universal, the moral law must be founded on the essential nature of man, that is to say, on the properties and qualities found constantly in the human being, and that distinguish him from other animals.” To be well assured, “morality presumes a science of human nature.”[13] The principle of ancient philosophy reappeared in the works of rationalists of the nineteenth century. Wilhelm von Humboldt declared that “the ultimate ideal of man, the ideal prescribed for him by the irrefutable and eternal laws of reason, consisted in a development as harmonious as possible of all his qualities in their entirety.” The modern historian, Lecky,[14] defines the aim of life as the full development of all that exists in the proportions determined by nature. Philosophers and historians are not alone in the adoption of Greek rationalism. Many naturalists, and among these some very distinguished authors, have spoken in the same sense. It is easy to see the Greek principle in such phrases as those of Darwin[15] when he wrote: “The term general good may be defined as the means by which the greatest possible number of individuals can be reared in full vigour and health, with all their faculties perfect, under the conditions to which they are exposed.” Georges Seidlitz,[16] an advocate of the great English naturalist, got still nearer to the conception of the ancients. According to him, the moral and rational life consisted in “the accomplishment of all the functions of the body, in due but full proportion.”