You obviously mean which scriptures we take to be literally true and which we take to be figuratively true. Most Christians believe the entire Bible to be true in some way. To answer your questions, some passages are clearly figurative, such as Jesus saying " I am the bread of life " - not many Christians think Jesus is a piece of bread. Like Aesop's fable of the tortoise and the hare, truth can be found even if the story is not literally true. Also, if there are contradictory passages, or paradoxes as I see them, such as the two Creation stories in Genesis, then I assume that figurative meaning is implied. Finally, if a passage seems to have no figurative or poetic meaning, or does not seem extraordinary or outlandish, I take it to be literally true. Extra-Biblical sources can also be used to learn about historical events described in the Bible. However, Christians have different ideas on how to take different scriptures in the Bible, and my opinion is one of many.