There are two contrasting concepts for Trill. One is that the symbiont is essentially an alien person; however, the joined Trill still mixes the original person with the memories and some of the personality of the symbiont. Only a small percentage of Trill are joined, and being accepted for the process is considered an honor. For joined Trill, a symbiont's memories and to some extent personality are a synthesis with the existing Trill's personality. Joined Trill have been studied in the philosophies of "Star Trek", in particular whether a person is essentially the sum of their memories (the philosopher Locke's "memory theory"). This concept was explored in the "Star Trek:Deep Space Nine" television episode "". (see )