Later in his career, he studied at University College London where he gained his PhD on the topic of The Business Life of the Jews in Babylon, 200–500 CE.

Jacobs became Moral Tutor at Jews' College, London, where he taught Talmud and homiletics during the last years of Rabbi Dr Isidore Epstein's tenure as principal.

Instead, he struggled to find a synthesis that would accommodate Orthodox Jewish theology and modern day higher biblical criticism.

The work was originally written to record the essence of discussions held on its title's subject at weekly classes given by Jacobs at the New West End Synagogue, and resulted in some mild criticism (but not in any major censure) at the time.

Most of Jacobs' book titled We Have Reason to Believe[7] deals with such topics as proof of God's existence, pain, miracles, the afterlife, and election: ideas which were not in and of themselves controversial.

He also comments that, given the arguments of textual criticism, "no work of Jewish apologetics, however limited in scope, can afford to fight shy of the problem".

When this assumption was translated into a definite invitation by the College's Board of Trustees in 1961, the then Chief Rabbi of the United Kingdom, Israel Brodie, interdicted the appointment "because of his [Jacobs's] published views".

The British newspaper,[13] The Jewish Chronicle, took up the issue and turned it into a cause célèbre which was reported in the national press, including The Times.

The defecting congregation purchased the old St John's Wood synagogue building, and installed Jacobs as its rabbi – a post which he held until 2001[17] and to which he returned in 2005.

On his 83rd birthday, in the Bournemouth United Synagogue on the sabbath before his granddaughter's wedding, Jacobs was not provided the honour of an aliyah customarily given to the father of the bride, which gave rise to heated correspondence in the Jewish press including accusations of pettiness and vindictiveness.

A few months before he died, Jacobs donated his book collection to the Leopold Muller Memorial Library at the Oxford Centre for Hebrew and Jewish Studies.

In December 2005, a poll by The Jewish Chronicle of its subscribers, in which 2,000 readers made their nominations, voted Jacobs the "greatest British Jew" in the community's 350-year history in England.