In Homiletics and Pastoral Theology, WGT Shedd puts a plug in for catechising in addition to other types of Sunday school (he, in keeping with the conventions of his day, calls it “Sabbath-School”) instruction.
Indeed, he favors a combination of the two–“lay” instruction in Sunday school and pastoral catechesis. Thus he says:
The pastor should, therefore, combine catechetical with Sabbath-School instruction. While he enlists the active zeal of his best educated parishioners, in the Sabbath-School, he should show his own deep interest in this excellent institution, by personally generalizing its teachings, in the catechetical exercise, and thereby putting the crown upon its influence. The pastor who thus completes the work of the Sabbath-School teacher, will raise up a generation of exceedingly intelligent Biblical scholars.1
The reason for this, Shedd thinks, is that such generalizing catechesis helps knowledge to make the transition from a passive to an active possession, providing a form of argument for one’s professed faith–that is, a rational, logical ordering of the topics of religion. So he goes on:
It was once said of a very learned, and at the same time very logical, jurist, that his learning was continually passing from his memory into his judgment. His acquisitions were not merely passively held, but were used for the argumentative purposes of his profession. In like manner, the indoctrination of Sabbath-School scholars causes the contents of the memory to pass over into the reason and the judgment, and makes all the texts and passages that have been learned, subservient to an intelligent and self-consistent religious belief.
To illustrate, he draws a parallel with Kantian epistemology, thus incidentally showing the wide currency this philosophy still held in the 19th century.
Indeed, to borrow an illustration from the Kantean philosophy, the catechism does with the memorized contents of Scripture, what the understanding, by its categories, does with the passive contents of the sense. It reduces the scattered and manifold elements to compactness and unity, and converts the large and distracting variety of items into distinct forms and clear conceptions, so that the mind can take this great number of particulars all in at once, and feel their single and combined impression. The catechism enables the pupils to feel the force of the whole Bible, and of the Bible as a whole.
In other words, the Kantian categorical imperative here is: learn the catechism–but note that it only “works” if you’re learning the Bible itself first and foremost, and using the catechism not as an end but as a means for organizing what the Bible teaches.