A parable to illustrate the limits and progress of science and human knowledge.
There is a community of intelligent beings who live in a place they call Cognita. It's made up of two islands: Prima and Segunda. Collectively, they call themselves the Cognitians. Their world is composed of a variety of natural environments, full of life in a multitude of forms. All the life on the two islands (and the waters surrounding them) evolved from a single common ancestor. The Cognitians themselves descended from a single ancestor (the Proto-Cognitian) who was herself born of an earlier species of beings (the Pre-Proto-Cognitians or Precognitians). All Cognitians were born on either Prima or Segunda and none has ever ventured beyond them.