This songs meaning is that love can't be defined by chemicals. The songs meaning is wrong. Just because you don't know the causes doesn't mean they are not there. Love is defined as a strong physical attachment, after you get to know someone it slowly fades and many people become annoyed by the things they loved and yes there are chemicals that coincide with every behavior. You will think the feelings will last, but they never do and chemicals in the brain dictate every behavior. Sorry, science is always right when done with data driven analysis and can explain everything and faith is ignorant poison and not even a good fantasy and wrong!