I'm trying to write this in Chinese:
"Knowledge is a subset of true beliefs."
But I can't find a proper word for "beliefs."
Notice that 信仰 is faith. Faith has religious connotations; belief is neutral.
I would say:
I thus translate it because of the following reasons.
1) A belief is something that is not tested or proved.
2) Knowledge in natural sciences is something that passes lots of tests. But, it is still to a certain extent a belief; for there is no way to be sure that knowledge in natural sciences will not be disputed by new evidence.
Therefore, knowledge can be viewed as the collection of tested beliefs.
If you are referring to the meaning of followed picture, maybe you can say "知识是客观事实和主观认知交集的子集".