The traditional sub-division of Metaphysics into Ontology, Cosmology, Rational Psychology, common to all the great modern constructive systems. Precise sense in which metaphysicians adopt these divisions for the purposes of their own treatment of the subject. Relation of Cosmology and Rational Psychology to the empirical sciences. English philosophers, who have usually been imbued with a wholesome distrust of deliberate system-making, have commonly paid comparatively little attention to the question of the number and character of the sub-divisions of metaphysical philosophy. In the pre-Kantian eighteenth century it was not unusual to add a fourth division to Metaphysics, Rational Theology, the doctrine of the existence and attributes of God, so far as they can be deduced from general philosophical principles apart from the appeal to specific revelation. The whole process of scientific systematisation involves certain assumptions as to the ultimate nature of the facts which are system-atised.