mode of stating that his metaphysical discussions are disputes about words. As such no doubt they have their importance, the question being, What are the ideas associated with, or the mental phenomena to be classed under, certain terms which exercise extensive sway over the thoughts, feelings, and conduct of men? Let the metaphysician, then, take care of the road by which he proposes to pursue this end. Let him take heed whilst he is in pursuit of a proper definition of a certain term, of such a definition as will be acceded to by the student, that he does not embarrass himself and his reader by a multitude of other still less defined or definable expressions, which thicken the darkness and the difficulty, and conduct to dismay and to despair.

These simple observations will, I conceive, go some way towards illustrating the question, in what manner, if in any manner, demonstrative reasoning may be connected with and obtained in metaphysical and moral science. Logic calls our attention to the nature and force of terms; to those

forms of expression which are essentially connected with valid reasonings-reasonings to which the mind. assents through the very nature of the terms. Mathematical science exhibits the perfection of such reasoning and such terms. It works with symbols significant of certain clear and uniform notions of figures and magnitudes. In its higher branches it is indeed the very science of symbols; its results arising out of the conceived and admitted nature of the symbols themselves, and their uniform relations one with another.

Before saying a few words on the application of demonstrative reasoning to physical and metaphysical science, I cannot forbear remarking how groundless is the common notion that demonstrative reasoning is stronger than all other kinds of evidence,—than the evidence of the senses or of testimony;* a

* There is some logical impropriety in connecting the words demonstration and evidence, and in talking of demonstrative evidence. In demonstrative reasoning we trace the harmony subsisting among our agreed principles or admitted notions and conceptions, and the consequences or connected notions. The senses (and testi

notion which makes some men call for demonstration where it is evidently absurd to make that call, unless it be remembered that the nature of every proposition must determine the nature of the demonstration, or the kind and criteria of proof. But who shall undertake to demonstrate by any admitted criteria of proof that milk is white and the sky sometimes appears blue? These are simple instances of names attaching to the objects of sense, and all communion of mind depends on agreeing to give similar names to similar impressions. And what folly would it be when my servant testifies that a crowd is in the streets, or Mr. Smith is in the study, to ask him to demonstrate these affirmations and propositions. conduct of life depends upon notions and habitual statements which require no demonstration, no laboured process of inquiry and proof; and with the general language of human intercourse, the associated ideas are mony, which must be ultimately referred to impressions on the senses) evidence the existence of certain causes of sensation external to ourselves, independent of our own minds, and supply the fundamental conceptions from which we reason.

The

sufficiently clear and uniform for the harmony and happiness and the ordinary wants of society. But when men aspire to what is called science, then must they take heed of language, as the ladder on whose rails the foot must rest in every step of the ascent.

Now with regard to physical science, it is obvious man is simply the observer and registrar of external nature. "Homo est naturæ minister," is the short and obvious maxim of the natural philosopher, and it is evident that the sciences which we call inductive merely give us the combined results of human observation in various specified departments, arranged, classified, and marked, and mathematical science is essential to perfect our observations.

As we range the walks of time and space, every new object or relation which presents itself to attention, a new term, significant of that object or relation, must be given. That same term will suffice for the same object or its counterpart, when the mind meets with it again. And the uniformity and variety in nature gives rise to the uniformity and variety in the structure and use

of human language, which, as a whole, may be considered a mystical radiation from nature, imprinting its pictures upon the subtle ground-work of the mind. A term becomes general by being applied to many similar objects or impressions. The uniformity in the objects and processes leads us analogically to apply the term laws to the phenomena and processes of nature, as science in its various departments reveals and registers the order, succession, and character of these phenomena. Each science having its own peculiar phenomena to register, requires its own peculiar terms; nor can we, where new objects of perception, new relations of thought, are to be expressed and held forth to the contemplation of the mind, object to many new and therefore hard terms. But in these days the student of nature must be warned against supposing that a mere knowledge of terms is scientific knowledge, although it must be admitted as an indispensable and an unavoidable part thereof. The learner of a new science cannot but be as the child, whose