Judaism is not a missionary faith. It takes the attitude that there are many paths to God and that, to put it bluntly, it does not matter which one you take, so long as you get there in the end. It is true that some people choose to convert to Judaism, and that is certainly an option for those who so wish, but we do not go out looking for converts.
It means that most Jews are Jewish because they were born that way. For the last two thousand years, you have been defined as Jewish if your mother was Jewish. It is the so-called "matrilineal line" and was based on two assumptions: that you always know who your mother is, even if your father's identity might be less certain; and that it is the mother who sets the tone of the home and guides its spiritual direction.
But while this might have been appropriate in a bygone age, it is no longer right for today. Fathers play an active role in the atmosphere of the home and the upbringing of the children. Just as it is sexist to deny women an equal role in the workplace, it is also discriminatory to dismiss men's domestic influence.
Moreover, until modern times, most Jews married fellow Jews, so both parents were Jewish, family life was entirely Jewish and children were brought up in an exclusively Jewish environment. In 21st century Britain, though, as elsewhere in Europe and America, there is a high rate of mixed-faith marriage which affects people of all faiths, including Jews.
This has created a major anomaly: if a Jewish family has two children, a boy and a girl, and both choose non-Jewish partners: then the children of the daughter will be Jewish even if they have no Jewish education, whereas the children of the son will not be Jewish even if they have a strong Jewish upbringing.
The latter is not a theoretical situation but affects tens of thousands of individuals. They have a Jewish heritage but not a Jewish passport. It denies them their identity, while it also denudes the Jewish community of its future.
That is why the Assembly of Reform Rabbis UK decided that from now on a person with one Jewish parent - of whichever gender - is eligible for synagogue membership. Ideally they should also have a Jewish education and be engaged in Jewish life, although the fact that they wish to join a synagogue already indicates their sense of belonging.
Still, it is not entirely a revolution: in the Bible, a patrilineal system operated - you were Jewish if your father was Jewish. Thus Joseph married the daughter of an Egyptian priest and Moses' wife was the daughter of a Midianite priest, but their children were still Jewish. It then became switched to the mother's line, and indicates that there has always been change as Judaism adapts to new circumstances.
What we are doing today is marrying the two systems - the original patrilineal and later matrilineal - and advancing a new equilineal one. The object is to be inclusive, extending Jewish recognition to those previously disenfranchised, and responding to the major social changes in Jewish life today.