Synderesis (Synteresis). A Greek term apparently introduced by Jerome and used throughout the Middle Ages to signify the scintilla or spark of conscience that was left in man when the rest of moral and spiritual awareness was deadened in the Fall. Because of this one remaining spark, God can gain access to fallen man and so redeem him. The concept was widely used in Christian mystical literature throughout the Middle Ages and later.

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989