Here is the final part of Chytraeus’ answer regarding the differences between Christian and non-Christian religion. He grants, as one also finds in Calvin (as Steven recently noted), that by nature there is some knowledge of God’s law–here Chytraeus focuses specifically on knowledge concerning the duties man owes to God. We see this in Plato and Homer. But the pagans (Cicero and Aristotle are taken as representative) did not sufficiently root their teachings on the virtues in God himself. It is not surprising that he charges pagans with almost total ignorance of the first table of the Law (though he does not deny that this is part of natural law; Chytraeus equates the moral law with the Decalogue and will later say that the sum [summa] of natural law [lex naturae] is comprehended [comprehensa est] in the Decalogue); it is perhaps more surprising that he also includes the sixth commandment, which for Chytraeus is “You shall not commit adultery,” among those matters about which natural knowledge has been so darkened and corrupted. In this regard, he differs from Calvin in the post linked above.
Praeterea etiam Legis Dei & virtutum doctrina apud Ethnicos mutila & manca, & mutipliciter depravata est, ut Cicero in officiis, & Aristoteles in Ethicis, ex professo virtutum explicationem instituentes, nullam fere mentionem faciunt Dei & primarum virtutum, Pietatais erga Deum, Timoris Dei, Invocationis, Gratiarum actionis, &c. quarum tamen noticiam aliquam natura in mentibus hominum lucere, Platonis etiam & Homeri sententiae ostendunt. Denique totius primae tabulae Decalogi & sexti etiam praecepti, noticia, & tota doctrina de interiore cordis immundicie, quam lex arguit, & perfecta cordis obedientia, quam lex flagitat, apud ethnicos plane obscurata & corrupta, & fere prorsus deleta fuit.
Moreover, the teaching even of the law of God and the virtues has been mutilated, maimed, and distorted in various ways in the writings of the gentiles, as Cicero in “On Duties” and Aristotle in the “Ethics,” professedly providing an exposition of the virtues, make almost no mention of God and of the principal virtues: piety towards God, the fear of God, the invocation of him, thanksgiving, etc. Nevertheless, that some knowledge of these things shines in the minds of men by nature the opinions even of Plato and of Homer demonstrate. Finally, the knowledge of the whole first table of the Decalogue and even of the sixth commandment and the whole teaching concerning the inner filth of the heart that the law censures, and the complete obedience of the heart that the law demands, in the writings of the gentiles has plainly1 darkened and corrupted and almost entirely wiped out.