Both Uses

principle
in
The Adventures of Huckleberry Finn
(Edited)

Full of principle.
Chpt 36

principle = basic rule or belief
Hain't you got no principle at all?
Chpt 39 *

principle = basic moral beliefs (beliefs about what is right and wrong that guide behavior)

Definitions:

(1) (principle)
a basic rule or belief
The exact meaning of principle can depend upon its context. For example:
- "our guiding principles" -- basic moral beliefs that guide decisions and behavior
- "electromagnetic principles" -- rules describing how the world works
- "She lacks principles." -- lacks moral guidelines
- "We agree in principle." -- about important basic beliefs
(2) (meaning too rare to warrant focus)
See a comprehensive dictionary for more specialized senses including one in chemistry.