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.
1. The Attic Greek word PISTIS is used in the sense of trusting.
2. The adj. PISTOS has the connotation of being worthy of trust.
3. In the Attic Greek, PISTIS was used as an abstract noun for confidence, trust, certainty, and conviction.
4. The Stoics used PISTIS for reliability or faithfulness.
5. In the Koine Greek of the New Testament PISTIS has 3 meanings.
a. As an attribute, or what causes faith, it is translated reliability or faithfulness.
b. As a non-meritorious system of perception, which emphasizes the object of faith, such as Christ in salvation, it is translated "faith."
c. It also means that which is believed, the content of faith, the body of belief, and so is translated "doctrine."
Ex: 2 Pet 1:1, Jude 3, 1 Tim 4:6, Gal 2:20 and Heb 11:1 Acts 6:7; Eph 4:5