Healthy multiplicity is the state of the body, where more than one mind can inhabit the body and coexist with each other peacefully. But between psychologists and the general population, multiplicity is more commonly looked at as a mental disorder, either as DID, MPD or DDNOS. There are few reasons for why multiplicity is currently viewed mostly from this perspective. One of those is that it is common to think that in one body there should be only one mind, because people are born with only one mind (or so you are told at least) and you have seen so many people with only one mind, so this can seem natural. The other is that multiples are usually badly portrayed in fiction, both in the sense that real multiples don't have some of the traits that are given to them and also in the sense that they aren't necessarily bad. Another reason is that, because of the previous reasons and how multiplicity is mainly viewed as a disorder, healthy multiples are reluctant to show themselves in real life, which further makes it easier to look at multiplicity as a disorder. And the last one is that some minds can have problem living together, but in most cases this is like when people in that have to live together have some problems doing so, but they shouldn't get diagnosed with a disorder for that and have all but one mind killed; instead they should go to someone and get help with their relationship, help them understand their differences and live with them.