Medieval writers spoke of a spark, scintilla, at the apex of the soul, which never consents to evil and always inclines toward God. Eckhart made it, or a power like it, the place of union, sometimes calling it uncreated. The image echoes the Stoic and Platonic divine seed in the mind.
Spark of the soul
The highest point of the soul, untouched by sin, through which it is united with God.
Also: scintilla, Fünklein