A soulmate is a person with whom one has a feeling of deep or natural affinity. This may involve similarity, love, romance, comfort, intimacy, sexuality, sexual activity, spirituality, or compatibility and trust.
In his dialogue The Symposium, Plato has Aristophanes present a story about soulmates. Aristophanes states that humans originally had four arms, four legs, and a single head made of two faces. He continues that there were three genders: man, woman and the "Androgynous". Each with two sets of genitalia with the Androgynous having both male and female genitalia. The men were children of the sun, the women were children of the earth and the Androgynous were children of the moon, which was born of the sun and earth. It is said that humans had great strength at the time and threatened to conquer the gods. The gods were then faced with the prospect of destroying the humans with lightning as they had done with the Titans but then they would lose the tributes given to the gods by humans. Zeus developed a creative solution by splitting humans in half as punishment for humanity's pride and doubling the number of humans who would give tribute to the gods. These split humans were in utter misery to the point where they would not eat and would perish so Apollo had sewn them up and reconstituted their bodies with the navel being the only remnant harkening back to their original form. Each human would then only have one set of genitalia and would forever long for his/her other half; the other half of his/her soul. It is said that when the two find each other, there is an unspoken understanding of one another, that they feel unified and would lie with each other in unity and would know no greater joy than that.