CONCLUDING OBSERVATIONS ON TERMINOLOGY. 751. We never sufficiently reflect that a language, strictly speaking, can only be symbolical and figurative, that it can never express things directly, but only, as it were, reflectedly. This is especially the case in speaking of qualities which are only imperfectly presented to observation, which might rather be called powers than objects, and which are ever in movement throughout nature. They are not to be arrested, and yet we find it necessary to describe them; hence we look for all kinds of formulæ in order, figuratively at least, to define them. 752. Metaphysical formulæ have breadth as well as depth, but on this very account they require a corresponding import; the danger here is vagueness. Mathematical expressions may in many cases be very conveniently and happily employed, but there is always an inflexibility in them, and we presently feel their inadequacy; for even in elementary cases we are very soon conscious of an incommensurable idea; they are, besides, only intelligible to those who are especially conversant in the sciences to which such formulæ are appropriated. The terms of the science of mechanics are more addressed to the ordinary mind, but they are ordinary in other senses, and always have something unpolished; they destroy the inward life to offer from without an insufficient substitute for it. The formulæ of the corpuscular theories are nearly allied to the last; through them the mutable becomes rigid, description and expression uncouth: while, again, moral terms, which undoubtedly can express nicer relations, have the effect of mere symbols in the end, and are in danger of being lost in a play of wit. 753. If, however, a writer could use all these modes of description and expression with perfect command, and thus give forth the result of his observations on the phenomena of nature in a diversified language; if he could preserve himself from predilections, still embodying a lively meaning in as animated an expression, we might look for much instruction communicated in the most agreeable of forms. 754.