I observe, then, that, if the idea of Christianity, as originally given to us from heaven, cannot but contain much which will be only partially recognized by us as included in it and only held by us unconsciously; and if again, Christianity being from heaven, all that is necessarily involved in it, and is evolved from it, is from heaven, and if, on the other hand, large accretions actually do exist, professing to be its true and legitimate results, our first impression naturally is, that these must be the very developments which they profess to be. Moreover, the very scale on which they have been made, their high antiquity yet present promise, their gradual formation yet precision, their harmonious order, dispose the imagination most forcibly towards the belief that a teaching so consistent with itself, so well balanced, so young and so old, not obsolete after so many centuries, but vigorous and progressive still, is the very development contemplated in the Divine Scheme. These doctrines are members of one family, and suggestive, or correlative, or confirmatory, or illustrative of each other. One furnishes evidence to another, and all to each of them; if this is proved, that becomes probable; if this and that are both probable, but for different reasons, each adds to the other its own probability. The Incarnation is the antecedent of the doctrine of Mediation, and the archetype both of the Sacramental principle and of the merits of Saints. From the doctrine of Mediation follow the Atonement, the Mass, the merits of Martyrs and Saints, their invocation and cultus. From the Sacramental principle come the Sacraments properly so called; the unity of the Church, and the Holy See as its type and centre; the authority of Councils; the sanctity of rites; the veneration of holy places, shrines, images, vessels, furniture, and vestments. Of the Sacraments, Baptism is developed into Confirmation on the one hand; into Penance, Purgatory, and Indulgences on the other; and the Eucharist into the Real Presence, adoration of the Host, Resurrection of the body, and the virtue of relics. Again, the doctrine of the Sacraments leads to the doctrine of Justification; Justification to that of Original Sin; Original Sin to the merit of Celibacy. Nor do these separate developments stand independent of each other, but by cross relations they are connected, and grow together while they grow from one. The Mass and Real Presence are parts of one; the veneration of Saints and their relics are parts of one; their intercessory power and the Purgatorial State, and again the Mass and that State are correlative; Celibacy is the characteristic mark of Monachism and of the Priesthood. You must accept the whole or reject the whole; attenuation does but enfeeble, and amputation mutilate. It is trifling to receive all but something which is as integral as any other portion; and, on the other hand, it is a solemn thing to accept any part, for, before you know where you are, you may be carried on by a stern logical necessity to accept the whole. – from An Essay on the Development of Christian Doctrine (1878)