How Can Religions Move Toward a Shared Spiritual Civilization? Religious Integration Without Conversion—From Doctrinal Difference and Shared Practice to the Generative Mechanisms of a Shared Spiritual Layer

Religion is one of the most enduring systems of meaning in human civilization. It responds to death, suffering, guilt, desire, hope, and ultimate meaning, while also shaping communal identity, ethical norms, ritual life, and intergenerational cultural memory. At the same time, religious traditions may differ genuinely and irreducibly on questions concerning God, ultimate reality, scriptural authority, salvation, liberation, post-mortem existence, and exclusive truth claims. If religious integration is understood as eliminating doctrinal difference, establishing a single scripture, or requiring believers to convert, it lacks a realistic foundation and is likely to generate new forms of identity threat. Within the framework of the Human Happiness Community, this paper reconstructs the idea sometimes expressed in Chinese as wan jiao gui yi - the convergence of religious and spiritual traditions - and proposes the Shared Spiritual-Civilizational Layer Model (SSCLM). Here, 'convergence' does not mean that all religions move toward the same name of God, the same scripture, the same ritual, or the same religious organization. It means that religious and nonreligious worldviews, while retaining their legitimate identities, may gradually generate an expanding shared spiritual-civilizational layer through intra-traditional deepening, interreligious translation, recognition of common human conditions, shared practice, mutual reflection, and sustained dialogue. The model distinguishes three levels. The first is the doctrinal-metaphysical level, where many propositions may remain different for long periods and this paper does not attempt to adjudicate their ultimate truth. The second is the ethical-practical level, where traditions may partially overlap in commitments such as reducing unnecessary harm, protecting life, honesty, justice, compassion, responsibility, peace, and ecological care. The third is the spiritual-civilizational level, where traditions use their own languages to cultivate more mature understandings of finitude, desire, suffering, otherness, death, responsibility, and self-transcendence, while gradually developing spiritual resources that can be shared across traditions. Scholarship on religious diversity has long distinguished exclusivist, inclusivist, and pluralist responses to religious difference. Even within pluralism, there is no single position: some accounts interpret religions as culturally different responses to a shared ultimate reality, whereas others resist reducing distinct traditions to one metaphysical foundation. This paper therefore does not begin from the premise that 'all religions are saying the same thing.' It locates the initial basis of religious integration at more observable levels: the shared conditions of human life, the practical outcomes of interreligious cooperation, traditions' capacity for self-correction, and whether interaction reduces hostility and improves the quality of shared life. The central argument is that the first step of religious integration is not to ask believers to leave their religions, but to enable them to go deeper within their own traditions while becoming more open to others. A shared spiritual civilization is not necessarily the result of religious differences disappearing. It can arise as a higher-order shared structure while those differences continue to exist.