Dr Frank Mobbs' letter (June AD2000) shows a misunderstanding of what I wrote in my article 'When is it infallible?' (May AD2000), and also a misunderstanding of the text he quotes - or rather, misquotes - from Vatican II.
He claims I doubt the authority of most of the ecumenical councils to teach infallibly. On the contrary, I am absolutely certain they can teach infallibly, and that they have done so on numerous questions.
In my article I was answering a difficulty, namely the claim that an ecumenical council with only a minority of the world's bishops present could be wrong in its teaching. I responded by appealing to the Church's subsequent acceptance of the doctrine involved, but I expressly said that this is not the only reply to the difficulty.
Later I used the words 'if it were suggested' in reference to a view that Nicaea might have been wrong through lacking sufficient bishops; I did not endorse the notion.
Why didn't I go on to show that such councils can teach infallibly? Because that involves a discussion of the extraordinary Magisterium, which was not the subject of my article.
Frank Mobbs also rejects my statement that Vatican II taught some things infallibly - through the bishops' exercise of the ordinary universal Magisterium. He says Vatican II saw this form of infallibility as operative only when the bishops are 'dispersed throughout the world'.
But that is not so. He has left out two key words. Vatican II says, 'even though dispersed throughout the world' (my italics). It would be remarkable if the bishops lost their ordinary universal infallibility when congregated together! I am not aware that any theologian has ever made such a startling claim.