There is a pressing issue on how converts are to be received into the Church from various groups. The main area of varying opinion is the reception of converts who received a baptism in the name of the Trinity, especially from Anglicans or Roman Catholics. The seem to be two contrasting positions with those who insist on not rebaptising and those who do, e.g. Mt Athos. There is also a third position that allows for either approach: that is rebaptising is acceptable, and generally preferred, but not rebaptising may be acceptable as an economy provided certain conditions have been met.
Which position(s) conform to the Sacred Tradition? Looking through the debates and variety of views held in the early Church in which one party held that we should not rebaptise, St Stephen and St Leo the Great, Popes of Rome, and the other that we should, St Cyprian of Carthage and St Firmillian. St Basil the Great recommends maintaining the custom of the local Church but favours rebaptism and that the form of baptism be at least that of the Church in all points of faith. The Saints seem to contradict themselves on a very serious matter. Is there a reconciliation of them or a common census to the matter by the Church? The answer is yes, although one that may not please those looking for a simple fixed approach.
Firstly, the Fathers accepted the Canon, and hence arguments, of St Cyprian of Carthage and thus rejected the argument of the Popes of Rome that insisted that the form of baptism must not be repeated because it can only be given once, even though it does not confer any grace or salvation to those receiving the form outside the Church. The Fathers held that the one Baptism of the Church is the one conferred by a Priest of the Church not only one application of the baptismal form. Outside the Church, there is no Holy Spirit and hence no Priesthood and so no baptism, that is no baptism that brings man to be a son of God. (Note: the dependance of baptism of the Priesthood; it is not a function of the laity.) Also, rejected by both St Cyprian and St Leo is any effect of baptism outside the Church, so at best the baptism is an empty form and nothing more. There was no sense that a baptism outside the Church caused the baptised to be “born again” nor to receive forgiveness of sins. Such a view is heretical because it is a denial of the Church and the mystery of one baptism.
However, the Fathers did not accept the position of St Cyprian without qualification. The Church, i.e. Christ, permitted converts from some heresies to be received only with Chrismation, i.e. by receiving the gift of the Holy Spirit. Thus, while the Fathers rejected the argument that the form could not be repeated by the Church, they accepted that the form could be received by the Church without repetition in certain cases and for the matter of economy. This is the position of St Basil the Great. This meant that the practices of those would insisted on not rebaptising did not affect the souls of those being received by Chrismation only and also enable certain converts of certain groups to be accepted without baptism, where there could be uncertainty about who baptised them but they knew that they received the form of baptism.
Where does this leave us with the converts of today? Canonically, all converts need to be baptised if they are not within the excepted groups mentioned by the Fathers in the Canons. However, following St Basil there is room for economy to be used in particular cases, such for example the Roman Catholics and this economy was used by various Fathers at times. This economy though does depend that the form of baptism, applied outside the Church, is the same as that of the Church and this is the major issue regarding the present forms of baptism used outside the Church, which are no longer exactly as the Church baptises (The form is not only the name of the Trinity but also three immersions in water each in one name of the Trinity. Also there should have been an anointing of oil and the baptiser could be a potential Priest). Although, there is still sufficient connection if the form used could be accepted as used in the Church for baptism by economy.
Although, as stated earlier, things are a bit vague regarding the limits of economy, i.e. the meaning of the same in all aspects of the faith, it would seem that the best option is to baptise all converts, excepting perhaps those from Uniate or recent schisms, who have exactly the same form of baptism. There is some room for those who are obstinate about already receiving a baptism to be received by Chrismation but there should be no rule that all members of a particular group should not be baptised on entering the Church. Also, any acceptance of some effect of the baptism outside the Church, that is outside the jurisdictions of canonical Orthodox Bishops, as somehow giving the baptised some connection to the Church should be rejected. This was thoroughly rejected by St Cyprian, whose the Fathers in the Ecumenical Councils accepted. There is no Priesthood outside the Church and hence no baptism, apart from empty form and this has been the consistent teaching of the Fathers both Eastern and Western.