Michael Reu, Catechetics: Or Theory and Practice of Religious Instruction, (Chicago: Wartburg Publishing House, 1931) p 44-45.
The catechumenate of the Early Church received its first blow when the heathen in large masses crowded to the baptismal font.
Still, a considerable measure of Christian knowledge was imparted and a reasonably thorough moral training was accomplished as long as the church insisted upon a careful examination of the baptismal candidates, upon a catechumenate of sufficient length, and, especially, upon thorough instruction during the competent period. Now, however, just these three essential conditions were increasingly disregarded. The preparatory catechetical discourse was discarded, probably as early as the fifth century. The time of a catechumenate was dangerously shortened.
Thus in 506 the Synod of Agde declared that Jewish converts must remain in the catechumenate for eight months; hence, ordinarily the time of preparation was still briefer (this action was taken because experience had showed that many former Jews withdrew from the church soon after they had joined). This, however, was not all. At the council at Bracara in 6100 time for low instruction of competentes was actually cut down to 20 days; and in most cases religious instruction was so completely overshadowed by ever increasing scrutinies that only a few formulae were memorized. That was all that remained of instruction which had one time had been conscientiously cultivated and cherished as an indispensable obligation of the Church. But all the alien elements adapted from paganism, the ceremonies and Magic formulae, were retained in the church. No wonder that this period produced large numbers of sacramentaries and liturgical treatises and books about the scrutinies, but very few catechetical writings.
The catechumenate decayed; it was buried under the scrutinies. This would perhaps have been less dangerous if conditions had been such that but few unbaptized adults remained within the precincts of the church; but the opposite is true: as the Roman Empire crumbled before the onslaught of the barbaric peoples, ever new pagan nations settled within the boundaries of the church which needed thorough instruction and training. The sad state of affairs was aggravated by the fact that even those baptized in infancy received no regular or sufficient training. A spiritually sterile church, poisoned by hierarchic thoughts with its emphasis on mystic-theurgic acts, was unable to renew these nations inwardly though she subdued them outwardly — with the help of the state.