[Chapter LXIX, Of Occult Philosophy, Book I. (part 4)]
It being shewed that there is a great power in the affections of the soul, you must know moreover, that there is no less Vertue in words, and the names of things, but greatest of all in speeches, and motions, by which we chiefly differ from bruits [brutes], and are called rationall; not from reason, which is taken for that part of the soul, which contains the affections, which Galen saith, is also common to bruits [brutes], although in a less degree; but we are called rationall, from that reason which is according to the voice understood in words, and speech, which is called declarative reason, by which part we do chiefly excell all other Animals. For λόγος [logos] in Greek signifies, reason, speech, and a word. Now a word is twofold, viz. internall, and uttered; An internall word is a conception of the mind, and motion of the soul, which is made without a voice. As in dreams we seem to speak, and dispute with our selves, and whilest we are awake we run over a whole speech silently. But an uttered word hath a certain act in the voice, and properties of locution, and is brought forth with the breath of a man, with opening of his mouth, and with the speech of his tongue, in which nature hath coupled the corporeall voice, and speech to the mind, and understanding, making that a declarer, and interpreter of the conception of our intellect to the hearers, And of this we now speak. Words therefore are the fittest medium betwixt the speaker and the hearer, carrying with them not only the conception of the mind, but also the vertue of the speaker with a certain efficacy unto the hearers, and this oftentimes with so great a power, that oftentimes they change not only the hearers, but also other bodies, and things that have no life. Now those words are of greater efficacy then others, which represent greater things, as intellectuall, Celestiall, and supernaturall, as more expressly, so more misteriously [mysteriously]. Also those that come from a more worthy tongue, or from any of a more holy order; for these, as it were certain Signs, and representations, receive a power of Celestiall, and supercelestiall things, as from the vertue of things explained, of which they are the vehicula, so from a power put into them by the vertue of the speaker.
Agrippa makes some import comments regarding language, for instance when he points out internal and external (uttered) aspects of words. When thinking of language for magical purposes, the internal aspect is very important. Imagination and imagery are core concepts of magic, and the it is important to understand that uttered words are symbolic representations of ideas; ideas that are often abstract. The spoken word is a physical symbol for the internal concept. In a very simply sense, speech (at least organized speech) is a willed act, and hence a magical act, making non-physical (internal) concepts into a physical symbolic form – which in turn can create change in the physical world (often via a causal chain of events that are set in motion – from hypnosis to commands to initiate a war).