namely, that of instruction, for which on an average a period of two years was required, and that of immediate preparation by prayer and fasting after the instructions had been completed. During the former period the aspirants were called κατηχοῦμενοι, _Catechumeni_; during the latter, φωτιζόμενοι, _Competentes_. As to their participation in the public divine service, the Catechumens were first of all as ἀκροώμενοι admitted only to the hearing of the sermon, and had thus no essential privileges over the unbelievers. They first came into closer connection with the church only when it was permitted them to take part in the devotional exercises, yet only in those portions which had reference to themselves, kneeling as γονυκλίνοντες, while also the congregation prayed kneeling. Only in cases of dangerous illness could baptism be given before the Catechumen had completed his full course (_Baptismus Clinicorum_). The Council of Neo-Cæsarea soon after A.D. 314 ordained that a Catechumen who as a γονυκλίνων had been guilty of an open sin, should be put back to the first stage of the Catechumenate, namely, to that of the ἀκροᾶσθαι, and if he then again sinned he should be cast off altogether; and the Œcumenical Council of Nicæa in A.D. 325 demanded that offending (παραπέσοντες) Catechumens should remain ἀκροώμενοι for three years and only then should be allowed to take part in the devotional service of the church.[98] § 35.2. =The Baptismal Formula.=--In close connection with the words of institution of baptism (Matt. xxviii. 19) and hence in a trinitarian framework, an outline of the doctrine common to all the churches, introduced first of all as a confession of faith professed by candidates for baptism, obtained currency at a very early date. Only a few unimportant modifications were afterwards made upon it, and amid all the varieties of provincial and local conditions, the formula remained essentially the same. Hence it could always be properly characterized with Irenæus as ἀκλινής, and with Tertullian as _immobilis et irreformabilis_. As a token of membership in the Catholic church it is called the Baptismal Formula or =Symbolum=. After the introduction of the _Disciplina arcani_ (§ 36, 4) it was included in that, and hence was kept secret from heathens and even from catechumens, and first communicated to the _competentes_. As the “unalterable and inflexible” test and standard of the faith and doctrine, as well as an intellectual bond of union between churches scattered over all the earth, it was called =Regula fidei= and Κανὼν τῆς ἀληθείας. That we never find it quoted in the Old Catholic Age, is to be explained from its inclusion in the _disciplina arcani_ and by this also, that the ancient church in common with Jeremiah (xxxi. 33), laid great stress upon its being engraven not with pen and ink on paper, but with the pen of the Holy Spirit on the