@Cassady (of course) covered a lot of ground really well. I’ll add some historical context that might help when explaining this to people.
The philosophical roots go back further than most realize. Plato’s Symposium (around 385 BCE) has Aristophanes describing humans as originally having four arms, four legs, two faces - and Zeus splitting them in half because they threatened the gods. That’s where the whole “searching for your other half” concept in Western romance actually comes from.
Although at this point, most people have probably heard it from TikTok. Or pop culture references like this or this. Not good.
Hindu traditions have Ardhanarishvara. Shiva and Parvati as a composite form split down the middle, representing masculine and feminine energies as inseparable. The Brihadaranyaka Upanishad describes the cosmic man splitting into male and female to create all life.
Jewish mysticism gets even closer to what we talk about here. Nachmanides wrote in the 13th century that God takes a soul and separates it into two halves, placing one in a male body and one in a female. The Talmud says 40 days before birth, a heavenly voice proclaims who your destined partner is.
You can find references in every religion, even in the Bible.