The Wordsmith's Forge

I meant 'viable' in the biological sense- especially in the older sense of "if it's possible to separate them and have one twin survive, it's better than both dying due to the medical issues". Not an accurate assessment, but the pervasive rule of thumb for a long time. From a medical standpoint, it's no more valid than saying all people with Cerebral Palsy also have speech defects, but that belief is also persistently pervasive.