Lyric discussion by Ashtray-girl 

Cover art for Modern Love lyrics by David Bowie

The religion thing seems pretty clear to me - faith should have never been institutionalised. Once it becomes an organisation, like church, dogmas arise and the whole faith turns into "being in church on time every sunday". Plus wars and power over people. David said that in interviews from 70s-80s that he believes in energy but he wouldn't put a name on it (God). I think that's because of the whole institution - church. The rest of the song is in my opinion about looking for a purpose in life. Like - you do lots of thing rather automatically and at the end of the day you question yourself if this is really what you're supposed to do, if this is how you want to fulfill your life. The modern love part is probably about commitment-free relationships that give you pleasure for a while and then leave you empty.