"The Church having received this preaching and this faith although scattered throughout the whole world. Yet as if occupying one house carefully preserves it. She also believes these points of doctrine just as if she had one soul and one and the same heart. She proclaims and teaches them and hands them down with perfect harmony as if she only possessed one mouth. For the churches in Germany do not believe or hand down anything different. Nor do those in Spain or Gaul. But as the sun, that creature of God is one and the same throughout the whole world; so the preaching of the truth shines everywhere enlightening all men willing to come to a knowledge of the truth"
Who was Irenaeus?
So wrote Irenaeus (AD130-202), the major theologian of the 2nd century Church. He had been instructed by Polycarp a disciple of John the Evangelist. His depiction of universal doctrinal uniformity may be exaggerated but equally it could not have been the case that the essential doctrines concerning the nature of faith and salvation could have uniformly been in error given that each of the churches he refers to could trace its origins just two or three generations back to the apostles.
They cannot ALL have interpreted Paul’s teaching wrongly. Yet their surviving writings bear little resemblance to the Protestant Reformers’ distinctive teachings or indeed the distinctive teachings of Augustine, who, particularly following his disputation with Pelagius came to reject any positive role for natural law in terms of innate spiritual faculties. Yet it is clear from their writing that such principles were understood by Irenaeus himself and fellow second century spiritual masters including Clement of Alexandria and Justin Martyr, later affirmed by the testimony of 3rd century Church historian Eusebius [note 1].
Not reliant on Scripture alone
It is not that all the churches of this period will have come to agreement through a sublimity of biblical exegesis. It is because the great apostle to the Gentiles himself or his direct appointees had founded and superintended a good number of these assemblies. These leaders understood Paul’s writings because they or their leaders had heard him and talked to him. They did not rely entirely upon his pastoral epistles that even his fellow apostle Peter observed were difficult and misunderstood by many (2Pet3:16).
Many of my own doctrinal assertions accord with these earliest Church Fathers, but not all. For as (third century) Origen later observed, the Church would come to explore and resolve certain mysteries over the course of her pilgrimage. But such progressive revelation cannot apply to the means of obtaining eternal life through Jesus Christ. That was clear from the start and has always been adequately set forth within the Apostolic Church. For Scripture makes clear enough that God wishes to heal all redeemable humanity and bring them to a knowledge of the Truth. To that end He has chosen a people to form a messianic community. Formed by divine teaching and empowered by His Spirit they are to bring light, healing and salvation to the world that He loves. In Paul’s words:
"The grace of God has appeared FOR THE SALVATION OF THE HUMAN RACE teaching us to deny ungodliness and worldly lusts to live sensibly, righteously and devoutly in the current age, anticipating the blessed hope and Shekinah of our Great God and the appearing of our Saviour Jesus Christ, who gave Himself for our sake so that we should be delivered from lawlessness and be purified as a SPECIALLY CHOSEN PEOPLE FOR HIMSELF burning with zeal to do good works. This is what you (Titus) are to say, rebuking with authority; let no man despise you" (Paul's letter to Titus ch2:11-15)
God’s reconciliatory purposes
That “specially chosen people” is the Church – but my book  systematically demonstrates from Scripture that it is God’s intention to reconcile humanity as a whole to Himself, not just the proportional few who are soul-healed (“saved”) in the present, being the elect of God. Natural law (so-called) plays an essential part in the broader reconciliatory process. The term is misleading for “natural law” in the anthropological context is not antithetical to divine grace. It pertains to God-given innate moral/spiritual faculties. That is evident in the functioning of the conscience, and is a form of common grace.
Such provides fallen humanity with a moral compass, a measure of restraint and crucially the ability to show compassion to others (which according to Jesus’ teaching in Matthew chapter 25 determines where the soul is heading after death). However, these innate spiritual faculties are incapable of saving the soul such that a person can relate to and serve the Creator whilst embodied within what Paul refers to as “the body of this death” inherited from our parents, ultimately from Adam.
The context of Christian salvation
Gospel salvation is to be born again through “the exceedingly abundant grace which is in Christ Jesus”. It is given to those “predestined to be conformed to Christ’s image“. That is so that they might serve as God’s royal priesthood whilst on earth and reign with Christ through eternity. This is worked out in some detail in my book  and, crucially, reconciled with the whole of Scripture.
 2nd century Church theologian, Irenaeus recognised that God in His providence is present with all “who attend to moral discipline, paying heed to the natural precepts of the law by which man can be justified“. [“Irenaeus against heresies” Book IV chap 13 para 1].
Justin Martyr spoke of God’s benevolence towards those who walk uprightly and in accordance with right reason. We have “a God who accepts those who imitate His own qualities of temperance, fairness and philanthropy and who exercise their free will in choosing what is pleasing to Him“. [First apology of Justin chaps. 43 & 46].
The witness of Eusebius (AD260-340) affirms such a perspective on free will and the role of natural law. Known as the Father of Church History, Eusebius documented the succession of the apostolic sees in East and West. He commented on the faithfulness (or otherwise) of some of their bishops. It provided an invaluable perspective on the doctrinal understanding of his time. In view of his own perspective on the matter, Eusebius indicates that the early Church subsumed a positive role for natural law within their theological/anthropological perspective when he wrote as follows:
The role of natural law
“The Creator HAS IMPRESSED A NATURAL LAW UPON THE SOUL as an assistant and ally in his conduct. It points out to him the right way by this law; but endowed by a free liberty, man makes the choice of what is best worthy of praise and acceptance; because he has acted rightly from HIS OWN FREE-WILL, when he had it in his power to act otherwise.
“As, again, making him who chooses what is worst, deserving of blame and punishment. By his own motion he had NEGLECTED NATURAL LAW; becoming the origin and fountain of wickedness, and misusing himself. And not from any extraneous necessity, but from free will and judgment. The fault is in him who chooses, not in God. For GOD HAS NOT MADE NATURE OR THE SUBSTANCE OF THE SOUL BAD; for he who is good can make nothing but what is good”.[Quotation from “The Christian Examiner”, Volume One – my highlighting]
 “The Little Book of Providence” – free PDF of e-book HERE