This book unlocks the Jewish theology of YHWH in three central stages of Jewish thought: the Hebrew bible, rabbinic literature, and medieval philosophy and mysticism. Providing a single conceptual key adapted from the philosophical debate on proper names, the book paints a dynamic picture of YHWH's meanings over a spectrum of periods and genres, portraying an evolving interaction between two theological motivations: the wish to speak about God and the wish to speak to Him. Through this investigation, the book shows how Jews interpreted God's name in attempt to map the human-God relation, and to determine the measure of possibility for believers to realize a divine presence in their midst, through language.