Religion and religiosity are once again playing a role in public discourse. However, religious beliefs are not monolithic blocks. Within each religion, there are varying degrees of belief, ranging from devout believers to moderate believers and non-believers. The practice of each degree of belief is crucially influenced by how seriously the believer takes the existence of God. Klaus Mai examines, using Christianity as an example, the concepts of faith and worldviews of significant philosophers and theologians in terms of their explicit or implicit stance on the likelihood of God's existence. The focus of his work is the development of a probability scale that can represent the identified degrees of belief in God's existence and their ideological differences. In his view, the foundation and core of moderate belief is the acknowledgment of a probability reservation for all religious statements regarding God's existence. Only moderate belief can ensure tolerance. The author rejects certainty of faith as a regression into magical thinking and advocates for a reason-oriented worldview combined with a rationally justified ethics.