There are many varying problematic binaries in The House of the Spirits, but a primary one is religion vs. science. Two of the daughters represent how science is constantly being mixed with religious concepts and their constant game of tug-of-war.

Rosa is just a bizarre but beautiful outcome of genetics yet she is constantly compared to an angel of sorts. The people are always looking for religion in things that have no religious implications at all. Clara, on the other hand, has mental powers that people can easily dismiss as the devil's work