What is Catechism?

Zacharias Ursinus was one of the primary authors of the Heidelberg catechism.
This article is found at the beginning of his commentary on this Reformed catechism under the heading,
“Special prolegomena with reference to the catechism”.
The electronic edition of this preface was scanned and edited by Shane Rosenthal.
It is in the public domain and may be freely copied and distributed.