406.
18.

Although it seems plain from our own consciousness, that the mind is an active self-moving principle or essence, yet capable of being moved, after its own manner, by other causes outward as well as inward; and although it must be obvious to reflection, that all its ideas, perceptions, and emotions, are, with respect to itself, of a spiritual nature--bearing such a relation to the spiritual substance in which alone they appear, as bodily motion is seen to bear to material substances; yet we know, from experience and observation, that they who are acquainted with words, are apt to think in words--that is, mentally to associate their internal conceptions with the verbal signs which they have learned to use.

And though I do not conceive the position to be generally true, that words are to the mind itself the necessary instruments of thought, yet, in my apprehension, it cannot well be denied, that in some of its operations and intellectual reaches, the mind is greatly assisted by its own contrivances with respect to language.

I refer not now to the communication of knowledge; for, of this, language is admitted to be properly the instrument.

But there seem to be some processes of thought, or calculation, in which the mind, by a wonderful artifice in the combination of terms, contrives to prevent embarrassment, and help itself forward in its conceptions, when the objects before it are in themselves perhaps infinite in number or variety.
19.