That Jewish culture did not play a huge part in his upbringing can be seen from the fact that he was baptized into the Lutheran church along with most other members of his class, and from his memory that he was forbidden from using Yiddish phrases at home.
It was at the Friends’ school that Frei saw a picture of Jesus and suddenly "knew that it was true" – this conversion experience led him to a form of Christianity which at this stage had nothing to do with attendance at church.
Later in his life, even when Quaker theology ran against the grain of his own thinking, he still found their meetings more satisfying than his adopted Anglican liturgies.
After three years, in August 1938, his parents left Germany, and Frei moved with them to the United States, where he was terrified by his encounter with New York City.
The family were very short of money, and were only able to find him a scholarship to study textile engineering at North Carolina State University (after seeing an advertisement for it in a paper).
He found himself drawn towards Anglicanism, towards what he saw as its more obviously 'generous' orthodoxy – to such an extent that in later life he was to say that Baptist ministry had always felt like a staging post on the way to somewhere else.
After the publication of two essays for a festschrift for Niebuhr in 1957 (including extracts from his thesis), and a short article on 'Religion, Natural and Revealed' in a handbook of Christian theology published the following year, there is a great gap.
Frei delivered a talk on Ludwig Feuerbach at the 1965 meeting of the American Academy of Religion, admittedly, but this does not seem to have been particularly central to his work.
In many ways he felt that the stands he had taken in his thesis against prevailing modes of apologetical and anthropocentric theology isolated him (again), made his work a struggle against the tide.
He did not have the temperament for the kind of sweeping statements and rabble-rousing clarion calls which might have pulled supporters to his side, and he produced his careful and complex writings only after taking great pains.
This strange project, an exercise in the rethinking of the structure and bases of Christology and, even though Frei soon developed doubts about various important aspects of it, it sets the tone and the themes for most of the rest of what he went on to say in theology.
Frei then entered another period of comparative silence, although this time it was not in complete obscurity: his name was out, rattling around in theological and historical circles attached to the massive and ground-breaking Eclipse, with Identity as a strange accompaniment.
His silence was not so much due to the pressures of teaching or to isolated and exhaustive research, but to his commitment to his job as Master of Ezra Stiles.
Firmly convinced theologically that he should have some kind of ecclesiastical grounding and location for his work as well as his academic setting, he nevertheless felt distanced from his adopted Anglican home, and yet committed to stay there.
In 1981, he spent some time in England during which he looked, on advice from Owen Chadwick, at visitation returns and sermons from the eighteenth century life of a couple of English parishes, hoping to find a way to combine the more social and cultural historical insights which these things gave him into the Christianity of the time with the insights he had hitherto gained through a more traditional study of well-known high-culture theologians and philosophers.
He prepared a contribution to Bruce Marshall's festschrift for George Lindbeck, and another for a conference on H. Richard Niebuhr to be held in September 1988.
Frei seems to have found a new theological confidence bubbling up with this historical project, however: now, more than ever, the two sides of his work (which had been the source of his ambivalence in the 1970s) become inextricably linked.
It is hard now to gauge exactly what shape the final project would have taken in which all this rich material would have been combined, but it is clear that Frei wished to pursue theological reflection through the medium of detailed historical work, and wished to hone a full-blown Christology of his own – a Christology which would have had a significant political dimension – by paying detailed attention to the ways in which Jesus had been described and redescribed in Western Protestant culture since the Enlightenment.