The Archbishop of Canterbury Rowan Williams on Thursday urged Catholics and Anglicans to set aside "second order" issues such as female clergy and the primacy of the pope in light of pursuing, "the fullest realization of communion," between the two bodies.

Speaking at the Gregorian University in Rome during a celebration of the centenary birth of Cardinal Johannaes Willebrands, the first president of the Pontifical Council for Promoting Christian Unity, Williams used texts from Willebrands and others to point to the solidarity among the two churches on "fundamental" issues including, "filial holiness and sacramental transformation," as a means of justifying moving towards communion in spite of other dividing issues between the two bodies.

"I am asking how far continuing disunion and non-recognition are justified, theologically justified in the context of the overall ecclesial vision, when there are signs that some degree of diversity in practice need not, after all, prescribe an indefinite separation," Williams said.

"At what point do we have to recognise that surviving institutional and even canonical separations or incompatibilities are overtaken by the authoritative direction of genuinely theological consensus, so that they can survive only by appealing to the ghost of ecclesiological positivism?" he continued.

Williams' speech was made during his first to the Vatican since the Catholic governing body announced in October that it was making official provisions to allow Anglicans into full communion with the church.

On the issue of clergy, the tenants of the provision do not allow female Anglican ministers to become ordained Catholic clergy, but allow for married Anglican clergy to become Catholic priests but not bishops. Catholic clergy are traditionally male, unmarried and celibate.

"Even if there remains uncertainty in the minds of some about the rightness of ordaining women, is there a way of recognising that somehow the corporate exercise of a Catholic and evangelical ministry remains intact even when there is dispute about the standing of female individuals?" Williams asked the gathering. "In terms of the relation of local to universal, what we are saying here is that a degree of recognizability of 'the same Catholic thing' has survived: Anglican provinces ordaining women to some or all of the three orders have not become so obviously diverse in their understanding of filial holiness and sacramental transformation that they cannot act together, serve one another and allow some real collaboration."

"All I have been attempting to say here is that the ecumenical glass is genuinely half-full – and then to ask about the character of the unfinished business between us," Williams said in conclusion. "For many of us who are not Roman Catholics, the question we want to put, in a grateful and fraternal spirit, is whether this unfinished business is as fundamentally church-dividing as our Roman Catholic friends generally assume and maintain."

"And if it isn't, can we all allow ourselves to be challenged to address the outstanding issues with the same methodological assumptions and the same overall spiritual and sacramental vision that has brought us thus far?"