Dream-time was, in the philosophical belief systems of the ancient aborigines of Australia, a kind of parallel timeline, or "time out of time," which coexisted with the objective world. The Dream-time was the realm of spirit beings, and of dreams. Mortals accessed the Dream-time through the Singing. By the end of the 20th century, only a small number of Australian natives maintained belief in the Dream-time. In time, these individuals learned to integrate their beliefs into the modern world, and by the mid 23rd century, it was considered as legitimate as any other theology.