Last week we examined some of the patristic writings of the early Church, principally St Vincent of Lerins who identified two ways by which the doctrine can be corrupted: either by addition (adding new strange doctrines that have no historical continuity with ancient Church teaching) or subtraction (when previously accepted teachings are suddenly jettisoned from the body of Church doctrine or declared obsolete). St Vincent of Lerins spelt out the importance of continuity as a hallmark of organic development, which could be likened to the growth of a seed:
 
In ancient times our ancestors sowed the good seed in the harvest field of the Church. It would be very wrong and unfitting if we, their descendants, were to reap, not the genuine wheat of truth but the intrusive growth of error. On the contrary, what is right and fitting is this: there should be no inconsistency between first and last, but we should reap true doctrine from the growth of true teaching, so that when, in the course of time, those first sowings yield an increase it may flourish and be tended in our day also.

Whilst it’s true that an acorn bears little resemblance to an oak tree, there is organic continuity: the acorn has contained within it all the essential characteristics of the mature oak tree. Yet, an acorn doesn’t instantly turn into a pocket watch, and any such claim that it did (by some stage magician, for example) would imply a clever sleight of hand or some other fraudulent deception. Authentic growth, like that of a tree, is gradual. Chopping down the oak tree and turning it into timber is change (one that it permanently destructive to the tree) and therefore such an act cannot be called organic growth, even though the timber comes from the tree. And the same holds true of church doctrine.

The Catholic understanding of the development of doctrine finds a middle path between the two extremes of stasis and change. On the one hand that faith of the apostles is not frozen or static, but it does have an inner stability and a coherence because it concerns the pursuit of religious truth, and truth itself is stable. If doctrine has no underlying stability and is entirely subject to change then it could end up contradicting itself from one time and place to the next. One of the most basic laws of epistemology (ie. the philosophy of knowledge and reason) is the ‘principle of non-contradiction’, namely, that “something cannot both be and not be at the same time”. For example, a mathematical equation can be either correct or incorrect, but it cannot be simultaneously correct and incorrect. Logically, God can either exist or not exist, but God cannot simultaneously exist and not exist. The same applies to religious doctrine: it can be either true or false, but not simultaneously true and false. Therefore, it is also impossible for doctrine to be true in some places but not others, or true in some centuries but false in other centuries. All truth claims necessitate consistency, including moral truths. The Ten Commandments are grounded in Divine Truth, therefore they have no expiry date. Murder can’t be immoral on Mondays, Wednesdays and Fridays but perfectly fine on the other days of the week. Nor can adultery be immoral in the 20^th century and suddenly moral in the 21^st century. Christ is the truth (John 14:6) and “Jesus Christ is the same, yesterday and today, and forever” (Hebrews 13:8).

While the underlying truth remains eternal and immutable (like God, because God is Truth) our human understanding on any given area of human enquiry can obviously grow. The whole scientific endeavour is one of a growing body of knowledge. Sometimes scientific theories are proven right, corrected or even disproven, but the underlying scientific reality is the same. Indeed, one of the necessary requirements for the scientific method of enquiry is the ability to repeat the same experiment and obtain the same results with 100% consistency. Hence one must be able to make the critical distinction between truth (which is complete and unchangeable) and the human attempt to apprehend truth which (when successful) is called knowledge. Because our knowledge can (and will!) grow over time we can expect to find a development (or ‘filling out’) in our body of knowledge; this growth will always be organic, in continuity with and building upon what was previously known.

St Thomas Aquinas, the greatest of the scholastic theologians, also explains the necessary continuity of the substance of faith. Thomas writes in the Summa Theologica: “As regards the substance of the articles of faith, they have not received any increase as time went on; since whatever those who lived later have believed, was contained, albeit implicitly, in the faith of those Fathers who preceded them. But there was an increase in the number of articles believed explicitly, since to those who lived in later times some were known explicitly which were not known explicitly by those who lived before them.” One example of this growth is the development of more refined theological language to understand the truths of faith. For example, the term ‘Trinity’ appears nowhere in the Bible yet it is universally accepted as a correct theological concept that is rooted in scripture and consistent with the Christian revelation that God is Father, Son and Holy Spirit. If the Church were to change the doctrine of the Trinity and declare there are now “four persons in one God”, this would necessarily mean that the previous doctrine of “three persons in one God” was incorrect. What is logically impossible is for both statements to be simultaneously correct.

In 1843, the celebrated Anglican priest and theologian, John Henry Newman converted to Catholicism. Two years later, in 1845, Newman wrote his “Essay of the Development of Christian Doctrine” (1845). The work was the fruit of many years of deep reflection on the necessary role of doctrine in the Church, and how the depositum fidei (deposit of faith) was expanded and developed over the centuries. His reading of the Church Fathers, including Vincent of Lerins, led him to realise that the faith of the early Church was none other than the faith preserved in the Catholic Church. This led him to offer his own careful exposition of how Christian doctrine develops, and why this is necessary. Newman writes:

The increase and expansion of the Christian Creed and Ritual, and the variations which have attended the process in the case of individual writers and Churches, are the necessary attendants on any philosophy or polity which takes possession of the intellect and heart, and has had any wide or extended dominion; that, from the nature of the human mind, time is necessary for the full comprehension and perfection of great ideas; and that the highest and most wonderful truths, though communicated to the world once for all by inspired teachers, could not be comprehended all at once by the recipients, but, as being received and transmitted by minds not inspired and through media which were human, have required only the longer time and deeper thought for their full elucidation. (J.H. Newman, An Essay on the Development of Christian Doctrine, page 20).

The endeavour of the Church to expound the deepest mysteries of our faith could never be achieved instantly, but required two thousand years of deep reflection from the greatest minds of all time. It is remarkable and shocking to me, the readiness of so many in the Church, to impulsively discard the entire edifice of Christian doctrine, on the grounds that 2000 years of collective wisdom from some of the greatest saints is now obsolete. The presumption that we ‘moderns’ have attained an enlightened religious understanding that none of our forebears knew that entitles us to change, mutilate and amputate important tenets of faith and morals that have been consistently reaffirmed over two millennia, reveals an embarrassing combination of ignorance and arrogance. As the Synod on Synodality draws to a close for 2023 many have been left thoroughly confused as to its purpose. Some are adamant that major changes to the Church are underway, including the ordination of women and the blessing of same-sex couples; others have played down the gathering as merely a dialogue. Either way the impression has been created that with enough lobbying and activism the Church is able to change aspects of her Doctrine that constitute the perennial and unchangeable doctrine of the Church. Those with an historically informed understanding of the Church realise that Christian doctrine is not something created by committees or lobbyists. Our Christian faith is something that is received and handed on according to the sense expressed by St Paul: “For I have received from our Lord that which I handed on to you” (1Cor 11:23). If we imagine that we are to hand on to the next generation of Catholics a faith that is different from that which the apostles received from the Lord then we cannot do otherwise than conclude that we will have created a new religion, one that our forebears would not recognise.

In conclusion, to answer our question: “Can the Church’s doctrine change?” I would answer:
If by ‘change’ we mean “becoming something new that it wasn’t previously” then it is categorically impossible for Church doctrine to change (according to the rule of faith and the law of non-contradiction). Doctrine doesn’t need to change because we ourselves are the ones called to change: to experience that holy conversion of heart, mind and soul to the will of God revealed in Jesus Christ: “Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.” (Romans 12:2)