The Philosophy of Natural Magic, by Henry Cornelius Agrippa, L. W. de Laurence ed. , at sacred-texts.com
It being shown that there is a great power in the affections of the soul, you must know, moreover, that there is no less virtue in words and the names of things, and greatest of all in speeches and motions; by which we chiefly differ from the brutes, and are called rational; not from reason, which is taken for
that part of the soul which contains the affections (which Galen saith is also common to brutes, although in a less degree), but we are called rational 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 excel all other animals. For logos, in Greek, signifies reason, speech, and a word. Now, a word is twofold, viz., internal and uttered. An internal 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 ourselves, and whilst 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 corporeal 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 virtue of the speaker, with a certain efficacy, unto the hearers; and this oftentimes with so great a power, that often they change not only the hearers but also other bodies and things that have no life. Now those words are of greater efficacy than others which represent greater things—as intellectual, celestial, and supernatural; as more expressly, so more 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 celestial and supercelestial things, as from the virtue of things explained, of which they are the vehicle, and from a power put into them by the virtue of the speaker.