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.
In this note I shall briefly summarise three class lectures on the psychological nature of religion.
1. Investigations into the psychological nature of religion date only from about the end of last century.
For ages previously men sought to know what religion was; but they attempted to find an answer merely by reflection on positive or objective religion. Kant opened up to them a new path—that of investigation into the nature of religion as an internal or mental fact. O. Pfleiderer's account (Die Religion, pp. 5-124) of the researches thus started characterised, and criticised.
2. The testimony of consciousness is sufficient to establish the existence of religion as a subjective or mental state, but cannot certify whether, as such, it be simple or complex, primary or derivative, coextensive with human consciousness, or wider or narrower, or whether there be anything objectively corresponding to it.
3. In order to analyse religion, the ultimate genera of consciousness must be ascertained, which has only been slowly done. History of the process: Plato, Aristotle, their followers, Descartes, Spinoza, the English philosophers from Bacon to Dugald Stewart, Kant and the German psychologists, Brown, Hamilton, and Bain. Establishment of the threefold division of mental phenomena into cognitions, emotions, and volitions. Difficulties of the division shown by the author in 'Mind,' No. V.