Having thus admirably laid down the rule of moderation and good taste, Erasmus goes on to details. He shows what kinds of words are to be avoided and to what extent. His comments on the use of obscene words are interesting in view of the general practice of his time and, indeed, upon occasion, of his own practice. Certain words are obscene because they represent obscene things; others because they are twisted from their harmless meanings. "What then is the principle of obscenity?--nothing more nor less than the usage, not of anybody and everybody, but of those whose speech is correct." Of himself it must be said that in general he lived pretty well up to his principles. Where he offends in this respect it is generally in a kind of composition, as, for example, in many of the Colloquies, in which he simply lets himself go, producing his effect by a freedom which he carefully avoids in other forms of writing. He was, if one may say so, artistically obscene. In spite of his admiration for pure Latinity, he does not hesitate to admit Greek words according to a rather dangerous canon. Greek words, he says, may be used when they are more significant, or shorter, or stronger, or more graceful, "for no Latin word can equal the grace of a Greek word." In short, "whenever any certain appropriateness [_commoditas_] invites us we may properly interweave Greek with Latin, especially when we are writing to learned men; but when we are not so invited and deliberately weave a discourse that is half Latin and half Greek, this may perhaps be pardoned in youths who are training themselves to readiness in both languages, but for men this kind of display is, in my judgment, far from becoming and is as undignified as if one should write a book in prose and verse mixed up together, as, in fact, has been done by some learned men." As to repetition, a trick of rhetoric often employed by Erasmus, he disapproves it in theory, but admits that it may be done "when the repetition helps the thought and when the weariness of it can be avoided by a certain variety." Cicero repeats, but he says "things similar, not the same things." "I insist upon this the more earnestly because I have heard preachers of considerable fame, especially in Italy, wasting their time in affected synonyms of this sort, as, for example, if one interpreting the word of the Psalmist, 'create in me a clean heart, O God!' should say, 'create in me a clean heart, a pure heart, a spotless heart, a stainless heart, a heart free from baseness, a heart unspoiled by vice, a heart purified, a heart made clean, a heart like snow,' and then should do the same in other words, this kind of _copia_ is not far removed from mere babble."