The contention that Esperanto is a natural linguistic system is discussed. Research is cited concerning universals of word order, dominant word order, polar type languages, Esperanto as a verb-subject-object language, and gapping in Esperanto. It is concluded that contrary to grammatical tradition, word order is not and cannot be completely free. This finding is especially important in the case of Esperanto where a logical system has been developed, but where the natural constraints of human languages have sometimes been overlooked. The research that is considered has implications for a theory of interlanguage and stimulates questions about the nature of topicalization and focus on Esperanto word order. (SW)