St. Cyril's writings were recommended to me some time ago as a good place to begin in my inquiry into Orthodoxy. Reading him again at this point in my journey is really interesting. I found his opening words here in his Fourth Lecture: On Ten Points of Doctrine to be beautifully written. I never used to get why the dichotomy was between true doctrine and good works, but now that's not such a mystery, nor is it offensive.
1. Vice mimics virtue, and the tares strive to be thought wheat, growing like the wheat in appearance, but being detected by good judges from the taste. The devil also transfigures himself into an angel of light (2 Cor. xi. 14.); not that he may reascend to where he was, for having made his heart hard as an anvil (Job xli. 24.), he has henceforth a will that cannot repent; but in order that he may envelope those who are living an Angelic life in a mist of blindness, and a pestilent condition of unbelief. Many wolves are going about in sheeps’ clothing (Matt. vii. 15.), their clothing being that of sheep, not so their claws and teeth: but clad in their soft skin, and deceiving the innocent by their appearance, they shed upon them from their fangs the destructive poison of ungodliness. We have need therefore of divine grace, and of a sober mind, and of eyes that see, lest from eating tares as wheat we suffer harm from ignorance, and lest from taking the wolf to be a sheep we become his prey, and from supposing the destroying Devil to be a beneficent Angel we be devoured: for, as the Scripture saith, he goeth about as a roaring lion, seeking whom he may devour (1 Pet. v. 8.). This is the cause of the Church’s admonitions, the cause of the present instructions, and of the lessons which are read.
2. For the method of godliness consists of these two things, pious doctrines, and virtuous practice: and neither are the doctrines acceptable to God apart from good works, nor does God accept the works which are not perfected with pious doctrines. For what profit is it, to know well the doctrines concerning God, and yet to be a vile fornicator? And again, what profit is it, to be nobly temperate, and an impious blasphemer? A most precious possession therefore is the knowledge of doctrines: also there is need of a wakeful soul, since there are many that make spoil through philosophy and vain deceit (Col. ii. 8.). The Greeks on the one hand draw men away by their smooth tongue, for honey droppeth from a harlot’s lips (Prov. v. 3.): whereas they of the Circumcision deceive those who come to them by means of the Divine Scriptures, which they miserably misinterpret though studying them from childhood to old age (Is. xlvi. 3.), and growing old in ignorance. But the children of heretics, by their good words and smooth tongue, deceive the hearts of the innocent (Rom. xvi. 17.), disguising with the name of Christ as it were with honey the poisoned arrows of their impious doctrines: concerning all of whom together the Lord saith, Take heed lest any man mislead you (Matt. xxiv. 4.). This is the reason for the teaching of the Creed and for expositions upon it.