Last Saturday the Jewish community came together to celebrate what is often referred to as the holiest day of the year, Yom Kippur. Synagogues were packed full as Jews atoned for the faults of the past 12 months and made resolutions to do better in the future.

But already the synagogues have emptied, and most are as denuded as churches the Sunday after Christmas. The usual suspect takes the blame. Secular culture is accused of seducing the absentees, either distracting them by leisure pursuits or weighing them down with exhausting jobs to secure a supposedly higher standard of living.

Nonsense. Those are just outer symptoms of an inner malaise. The real reason is that many Jews simply do not believe in God, while others are not sure if God exists; and even if God does, then to their mind, it is almost certainly not in the way depicted by organised faith.

What is so devastating is that these views are held not just by Richard Dawkins-followers, who have no connection with religious life and are already written off as lost to the community, but by the very people who do pack the synagogues every year.

The reality is that a significant percentage of Jews are atheists or agnostics. No wonder they do not come back to pray to a God they reckon is absent.

But are they still Jewish? On one level, Judaism is infused with the presence of God and for many Jews that is the unequivocal centre of their faith. Yet, in other respects, it is curiously indifferent to God.

Go to the very start of the Hebrew Bible to search for an explanation of God and you find that God is assumed and attention shifts instead to humanity. Turn to Genesis 12 to find out what made Abraham leave idolatry for monotheism, and it seems that God took all the initiative.

Step back and examine the total of 613 commandments that the rabbis counted in the Bible, and they are almost all concerned with human behaviour. It took almost 3,000 years before the Thirteen Principles of Jewish Belief were formulated by Maimonides, which suggests a certain lack of urgency. Hence the simplistic but pointed description of Judaism as a religion of deed rather than creed.

The nature of God was never defined or enforced. Is the Jewish God the fierce patriarch or loving nurturer? Is God the distant power behind the Universe or the intimate voice of conscience? Has God long ago left Creation to its own devices or is there still an active involvement? There is neither a consensus among Jews, nor any need for a consensus. The Jewish heretic was not someone who believed the wrong concepts, but one who broke Sabbath observance.

Even today, when asked what is the most important command, most rabbis either choose “Love your neighbour as yourself”, from Leviticus 19, or opt for Hillel’s reformulation in the 1st century: “Do not do to others what you would not have them do to you.” Either way, it is action rather than belief. It is how we treat each other that makes us Jewish, not what sort of God we have in mind.

This relaxed attitude to theology explains why, surprising as it may seem, Jews who are atheists or agnostics still consider themselves committed Jews and even attend services. They identify with Jewish history, or are embedded in Jewish culture, or aspire to Jewish values, albeit God-free.

Some rabbis may be appalled at this lack of religiosity, but while faith may be desirable, the peculiar reality is that it is only one aspect of Judaism; its absence does not necessarily disqualify membership.

Jewish atheists and agnostics abound, and it is time to acknowledge their existence. They adhere to the commandments even though they doubt the Commander. Frankly, that is what counts most. To be a good Jew does not necessarily mean believing in God, just doing what He says.

Rabbi Dr Jonathan Romain is minister of Maidenhead Synagogue and author of The Jews of England