MENTAL PHILOSOPHY.
1. The word Physics means etymologically the study of nature (phusis, nature); but even the ancient Greeks restricted the meaning of the term to the sensible or phenomenal properties of the material world. At present the meaning of Physics is still more limited: it now denotes that branch only of the Natural Sciences which explains the sensibIe properties of bodies in general, and the causes (such as gravitation, heat, light, magnetism, etc.) which modify those properties. It is thus distinguished from the sciences of Astronomy, Chemistry, Biology, etc., which deal specially with the sensible properties of only certain classes of bodies.
2. Metaphysics is the science of whatever is not sensible, of what lies beyond the reach of the senses, as far as it is cognoscib1e by human reason. It belongs to the genus science, -- i.e., the certain and evident cognition of things by their causes; and it is the highest among the purely human sciences, for it traces its knowledge to the highest causes accessible to human reason. Its specific difference lies in dealing with whatever is beyond the reach of the senses, the non-sensible being its formal object; whether this be found in spiritual beings, totally beyond the reach of sense, or in material things in as far as these do not affect the senses.
3. What sensation cannot perceive is the formal object of our mind or intellect, the special functions of which are abstraction and generalization; therefore abstract and universal knowledge, as such, is the formal object of Metaphysics. Hence this science, being distinctively intellectual, is also denominated 'Intellectual Philosophy,' or 'Mental Philosophy'; while the application of these abstract truths to the moral conduct of men is styled or 'Moral Philosophy.'
4. Metaphysics is divided into two parts: 1. General Metaphysics studies the non-sensible in general, its principal object is 'being,' as such; it is therefore called Ontology, or the science of being (onta, beings). 2 Special Metaphysics studies what is peculiar to special classes of beings; it comprises Cosmology, which treats of the material world (kosmos, the world); Natural Theology, which treats of the knowledge of God (Theos, God), as far as He is knowable by merely natural means; and Psychology, which treats of living things (psuchê, the vital principle), especially of the human soul. Metaphysics does not treat professedly of the Angels, because their existence is not known to us except by Revelation. Some modern Metaphysicians, confining Psychology to the study of the human soul, treat separately of organic bodies under the title of 'Organology,' or 'Biology' (bios, life). Others consider all that is peculiar to man under the head of 'Anthropology.' The division which we have given above is the oldest and, even now, the most commonly adopted.