Go back to first year studies of faith. Pistis is also known as doctrine.
The usual translation is faith or faithfulness. Not doctrine. It could mean the conviction of the truth of anything that you could care to name.
http://www.biblestudytools.com/lexicons/greek/kjv/pistis.html says that: conviction of the truth of anything, belief; in the NT of a conviction or belief respecting man's relationship to God and divine things, generally with the included idea of trust and holy fervour born of faith and joined with it.
Pistis does not mean what you say it means.