To be Jewish, according to the prevailing view, it is enough to have a Jewish mother (or to have been converted by an approved Orthodox rabbi). Belief in one supreme creator of the universe, in the Torah as the word of God, and in Jewish ritual need have nothing whatever to do with Jewishness. (We ignore here the many problems with this conception, such as: how can there be a secular Judaism?)
The definition of Jew has been bitterly controversial inside and outside of Israel since its founding. The point is, as anthropologist Roselle Tekiner wrote, "When the central task of a state is to import persons of a select religious/ethnic group – and to develop the country for their benefit alone – it is crucially important to be officially recognized as a bona fide member of that group.