(Barzakh). Barrier or isthmus or separating partition. The barzakh is the symbol of an intermediate state. It is something which separates two other things while never going to one side. It is the barrier between the known and the unknown, the existent and the non-existent. Imagination is the most excellent barzakh in that it is 'neither this nor that', or 'both this and that', or the realm of 'He/not He' (Huwa/la Huwa).
"It is He Who has let free the two bodies of flowing water: One palatable and sweet, and the other salt and bitter; yet has He made a barrier between them, a partition that is forbidden to be passed" (25:53) .
Isthmus