The Rev David Scott is right to say that when church leaders speak out together they carry more weight and give a powerful ecumenical witness to the nation (Letters, May 10).

This is so when a common mind is reached on issues of the day in the light of the Gospel we hold together and proclaim. We could do more of it and, in this respect, I am fully with him.

When it comes, however, to matters which are not so much of opinion but of truth, then our divisions, particularly on the nature and authority of the Church, impede our effectiveness.

The role of a bishop in the Catholic Church is not primarily to express an opinion, whether his own (which he is perfectly entitled to hold) or that of his people (when such can be gauged) but to bear witness to, and interpret in the context of life today, the truths which have been handed down to him – to hold to the Tradition of faith and practice and to proclaim it.

The present argument over gay marriage is a case in point.

There is no doubt that the Presbyterian system finds difficulty in this regard when addressing moral questions which were either unasked at the time of the Reformation, or went wholly unchallenged.

Tradition cannot be placed in the arena of opinion in the same way as issues of social reform or political expediency.

(Most Rev) Mario Conti,

Archbishop of Glasgow,

196 Clyde Street,

Glasgow.

Harry Reid's column contains inaccuracies ("Our churches should speak out with a single voice", The Herald, May 8).

He suggests the Church of Scotland has "more or less given up on any attempt to be Scotland's national Church". In 2010 the General Assembly voted overwhelmingly to retain that status.

Not only does that mean we are committed to having a church in every parish in Scotland, it also means the church is there to serve all the people of Scotland who wish to use its services. That territorial responsibility is also what constitutes a national church.

He also suggests that "moderators rarely speak out publicly".

Since my appointment last May I have spoken out about sectarianism. On this we are united with the Roman Catholic Church and we are still working closely with the Scottish Government on this blight upon our nation.

I have also written for national newspapers on knife crime, poverty, the importance of community, the massacre of young people in Norway, the oppression of the Palestinians and the war in Afghanistan.

More recently I addressed the STUC conference in Inverness on the topic of the economy after a report from our Church and Society Council was published. This report was praised in a leader in The Herald.

Rt Rev David Arnott Ma BC,

Moderator Church of Scotland,

121 George Street,

Edinburgh.