According to Osho, ultimately there is one universal soul (Brahman); what appears as many “souls” are one consciousness expressing through countless gross and subtle bodies. Individuality persists while the subtle body of desires and impressions remains; with liberation (moksha) the subtle body dissolves and the drop merges into the ocean. Thus multiplicity is in vehicles only—unity is the truth realized beyond the subtle.
It’s like one electricity lighting many bulbs: we seem separate because of our bodies and inner patterns, but when those patterns end, only the one light remains.