According to the Lonely People Songfacts,this was written by Dan Peek, who was one of the 3 original members of America. Many of Peek's compositions show a very spiritual and searching side and "Lonely People," is one of those songs and easily his best-known.
This is for all the lonely people
Thinking that life has passed them by
Don't give up until you drink from the silver cup
And ride that highway in the sky