METAPHYSICS, a word of uncertain origin, but first applied to a certain group of the philosophical dissertations of Aristotle (see ARISTOTLE). As since employed, it has had various significations, and more especially two—a larger and a more confined. In the more confined sense it is allied to the problems of the Aristotelian treatise, and is con cerned with the ultimate foundations of our knowledge of existing things. What is the nature of our knowledge of the external world, seeing that mind cannot properly know what is not in contact with itself ? has been asked by philosophers, and answered in various ways; and this is the great question of metaphysics (see PERCEPTION, COMMON SENSE). The name " Ontology" has been applied to the same inquiries into our cog nizance of existences out of ourselves. But as the solution of this difficult question was found to involve an investigation into the nature of the human mind, it became allied with the science whose object it is to describe fully aud systematically the laws and properties of our mental constitution—a science called by the various names of psychology, mental philosophy, moral philosophy; and hence metaphysics came to be an additional name for this more comprehensive department. The word is employed
at the present day by writers of repute in both meanings. Thus, Ferrier's Institutes of Metaphysic is occupied solely with the questions connected with knowledge, or the nature of our perception of an external world; his explanatory title is, The Theory of Knowing and Being. On the other hand, Mansel's metaphysics is divided into two parts—PSYCHOLOGY, or the science of the facts of consciousness, which expresses the science of mind generally; and ONTOLOGY, or the science of the same facts considered in their relation to realities existing without the mind—that is, the problem of percep tion, or metaphysics in the narrower sense.