and authority in the development of society," and "conservatism and progress." The most adequate historical proof and illustration of the truth in question as to the nature of social evolution will be found in the Earl of Crawford's 'Progression by Antagonism' and 'Scepticism and the Church of England.' NOTE VI., page 32. DEFINITION AND CLASSIFICATION BY THE HIGHEST TYPE. Dr Whewell maintained that in natural history groups are fixed not by definition, but by type. "The class," he wrote, "is steadily fixed, though not precisely limited; it is given, though not circumscribed; it is determined not by a boundary-line without, but by a central point within; not by what it strictly excludes, but by what it eminently includes; by an example, not by a precept; in short, instead of Definition we have a Type for our director. A type is an example of any class--for instance, a species of a genus--which is considered as eminently possessing the characters of the class. All the species which have a greater affinity with this type-species than with any others form the genus, and are ranged about it, deviating from it in various directions and different degrees."--Philosophy of the Inductive Sciences, vol. i. pp. 476, 477. Dr Whewell, it will be observed, was more cautious in his language than the theologians to whom I have referred. He did not speak of defining by type, but only of classifying, not by definition, but by type. His motive, however, for entertaining the view he laid down, was obviously the same which has led so many theologians to give definitions of religion which are only applicable to its highest forms. Probably it was insufficient. Prof. Huxley (Lay Sermons, pp. 90-92) very justly, it seems to me, argues that classification by type is caused by ignorance, and that as soon as the mind gets a scientific knowledge of a class it defines. Nothing which is not precisely limited is steadily fixed; nothing which is not circumscribed is exactly given: if the boundary-line is not determined, the central point cannot be accurately ascertained; what is eminently included cannot be known so long as what is strictly excluded is unknown. While assenting to the view of Prof. Huxley in the passage indicated, I may remark that he falls into one error which rather forcibly illustrates what is said in the page to which this note refers regarding the necessary poverty of the significance of a strictly scientific definition of an extensive class. He instances as a definition which is of a truly scientific kind and "rigorous enough for a geometrician," the following: "Mammalia are all animals which have a vertebrated skeleton and suckle their young." But clearly this definition says too much if we are to criticise it rigorously. Were it true, there would be no males among mammalia. The definition is in strictness applicable to females only. NOTE VII., page 38. PSYCHOLOGICAL NATURE OF RELIGION.