It seems like a reasonable question. Other religions have basic tenets that a person must confess or state as their beliefs in order to be considered a member of the faith. For most Christians, belief in the divinity of Jesus and his resurrection is a foundational belief that defines the religion. For Muslims, there is the Shahada, the declaration of faith in one God and that Muhammad is God's prophet.
But, what about Judaism? Is there anything that Jews are required to believe? Something that is so indispensable that, without it, you cannot call yourself a Jew?
The question is harder than it seems because Judaism, even in its most traditional form, insists that Jewish identity is immutable. Once you are born a Jew or convert to Judaism, there is nothing that will make you stop being a Jew. Even believing in another religion will not take away your Jewish identity.
However, Judaism does insist that just being a Jew is not enough. A Jew, says the tradition, must believe in some basic ideas, even if failing to do so will not remove Jewish identity. In the twelfth century c.e., Rabbi Moshe ben Maimon (known as Maimonides and as the Rambam) wrote his famous Thirteen Principles of Faith, which include belief in a single, unified, eternal, all-knowing God who is the only true God, belief in the Torah and the prophets as true teachings of God's will, and belief in the redemption of the world. (Fun fact: the words of the song Yigdal are actually a poetic rendering of the Rambam's 13 Principles).
The thing about the Rambam, though, is this: He himself did not believe in the Thirteen Principles as literal facts. A careful reading of his works shows that he understood the ideas of God, revelation and redemption on philosophical and metaphorical levels. He wrote dismissively of the idea that God has anything like a body, a personality, or any human attributes. To the Rambam, God is the abstract idea of perfection and ultimate meaning. What is more, the redemption of the world, to the Rambam, will not be a supernatural event filled with miracles, but a natural occurrence of a time in which all people will live in peace.
So, what are we supposed to believe, beyond the abstract and general belief in a divinity beyond ourselves and a belief that human beings came somehow, someday live in peace? Aren't there some specific things that Jews really need to believe about God, about ourselves, and about how we treat other people? I think there are.
Here is how I think about it:
1) Repeated throughout Judaism's most sacred texts is the command to care for the most vulnerable. To be a Jew is to have compassion for the slave, the impoverished, the bereaved, the destitute, and the despised. We are also commanded to provide them with the physical and spiritual comforts they require. More importantly, Judaism cannot permit an attitude that blames the poor for their poverty or that despairs that we are unable to alleviate their suffering. Jews believe in action for those in need.
2) Judaism is a religion of joyfulness. Each morning we should reawaken to the miracle of the world that has been given to us. While sadness and depression are real experiences that cannot be avoided at times, we are commanded to live with hope for the good and with a determination to find delight and wonder in the world.
3) The most fundamental Jewish belief about God is this: God is the unity that connects us all to each other and to everything. We human beings are not the center of the universe, but we are a part of it. We live with a moral imperative to recognize that there is a truth beyond ourselves that we must strive to obey. There is hope for this world to live up to its aspirations of justice and peace because the world exists for a purpose that we cannot fathom, but that makes us believe.
So, believe it or not, there are some things that we should believe as Jews. It may not be a catechism or a list of rules. It is more like an attitude, an appreciation, and an aspiration for the way the world ought to be.