The necessary art of expressing them

Erasmus, De ratione studii, 1511, translated for the first time into English by William Harrison Woodward, 1904:

All knowledge falls into one of two divisions: the knowledge of truths and the knowledge of words—and if the former is first in importance, the latter is acquired first in order of time. They are not to be commended who, in their anxiety to increase their store of truths, neglect the necessary art of expressing them. For ideas are only intelligible to us by means of the words which describe them; wherefore defective knowledge of language reacts upon our apprehension of the truths expressed. We often find that no one is so apt to lose himself in verbal arguments as the man who boasts that facts, not words, are the only things that interest him.