If by "alone" you refer the five solas where it says by grace alone faith alone and so on, it is a protestant invention they came up with to push back against the abuses of the roman catholic church.
The idea of faith alone is completely unbiblical as the only times you find the words "faith" and "alone" in the same verse is in James, where the teaching is refuted.
The thing about faith is, it is never ever alone, because faith worketh by love and if you have faith, it will manifest it some way. Now: ALL protestants believed this, they believed that dead faith saves no one, but why did you make a sola fide then? Because it sounds catchy and its something to make a separation to the catholic church with.
How about this: get rid of infant baptism, now thats a good way to separate.