This paper describes a study that investigates the varieties and evolution of nothingness-qua-being 無即有 and being-qua-nothingness 有即無 in Hajime Tanabe's philosophy of religion (from Philosophy as Metanoetics to Philosophy of Death). Nothingness-qua-being means that absolute nothingness saves beings by mediating them. Being-qua-nothingness means that beings become intermediaries of absolute nothingness and cooperate with it to save other beings. Nothingness-qua-being and being-qua-nothingness constitute the pivot point of the relation between religion and ethics, which is Tanabe's lifework. Nothingness-qua-being, from Philosophy as Metanoetics to Demonstratio of Christianity, means that absolute nothingness works by mediating beings who are ...