The modes of substance are those dis tinguishable objects of sense which might, if separate, produce simple ideas. Thus, softness, fragrance, yellowness, and acidi ty, are among the modes which co-exist in the subject oe substance, lemon. Many distinctions are made in modes. They are called essential or accidental, abso lute or relative, &c. The moderns ap pear to use the words properties of bo dies, and powers and laws of nature, with much more distinctness than the earlier logicians did their modes and ac cidents.
Words are intended to be the signs of things, but are very far from being so. If our ideas were adequate representations of the things which cause them, which they are not ; if they were not of necessity mutilated by abstraction, and there were not a continual exertion in language to emulate the rapidity of thought, then might words obtain the supposed resem blance. But the boasted extent and per spicuity of the intellect of man proceeds hut a littie beyond the signs and tones of those inferior animals who are supposed to have no power of conversing. And even if we could vanquish the insupera ble difficulties which impede our clear mutual communication, what ate the grounds of our knowledge ? they are very limited, and often fallacious.
Knowledge consists in the determina tion of those modes of surrounding be ings which are taken to be permanent, and of those which are observed to vary. The former are chiefly of the nature of quantity and position, and the latter seem resolvable into motion. Mathematical science appears to comprehend the whole of the first ' • and the latter, which em braces by far the greater part of what concerns our existence and well-being, is included in those histories of events upon which we establish our principles of cause and effect. Abstraction, or analysis, can give us very clear notions of the subjects of mathematics ; and in these alone it is that we find absolute proof or demonstra tion. But in all the rest of our knowledge the facts are complex, obscure, and of uncertain evidence ; and the principal, nay the only, ground of our reliance upon our doctrines respecting them is, that our predictions are in many.instances verified.
Words being constructed and establish ed by mere usage, are not only inadequate and contracted in their use, but equivo cal and synonimous ; that is to say, one word may be used to denote several dis tinct and different things ; as when we speak of a beam of light, a beam of tim ber, or the beam of a pair of scales ; or, on the contrary, as when we speak of an house, an habitation, or a residence. It
must be admitted, however, that there are few synonymes in the practice of those who are masters of a language ; be cause few words are consecrated by usage to precisely the same meaning.
Many acute and useful disquisitions have been written upon language and uni versal grammar. See LANGUAGE.
Since our idea of a thing must be com posed or made up of all the simple ideas which that thing can produce by our per ceptions, and this will for the most part be inadequate, the word, denomination, or name of a thing, must be the sign of that idea; liable to such additional error as may arise from any improper use that may be made of it. And as by abstrac tion we generalize our ideas and notions, and afterwards comprehend and compare them at our pleasure ; so in the COTISUUC tion of language a like order is fidlowed in words. Thus we may arrange things, from their similitude, under classes more or less abstracted as to their modes, call. ing these classes by the names of genera and species. And in the names of things, we shall have not only to regard this ar rangement, but likewise the appropria tion and correct use of the denomination itself If we had terms for all simple ideas, and were to enumerate in due or der all the simple ideas subsisting in a thing, that enumeration would constitute what is called a definition of the thing ; and simple ideas would be, as in strictness they are, undefinable. But since all our sensations are complex, the relations of simple ideas with regard to each other, as residing in the same subject, will afford the means of indicating them. Thus, light is that by which the organ of vision is acted upon, and the word is therefore defined or indicated from that organ Co. lour is a mode of light perhaps too sim ple to be defined, but clearly indicable from any natural subject in which it may subsist ; as, for example, green is the co lour of grass, red is the colour of a rose, and yellow the colour of an orange.