How do you know?
"How do you know that what you read is true?" . . . This is as difficult to answer as, "Where does Life come from?" You can begin by paying attention to your experiences. Listen to your inner sense of what is worth listening to. See if it works for you. Something someone has said or written has caught your attention. Now you want to know more about it.

What did that experience feel like in you?  Pay attention to it.  Something happened within you that causes you to seek further wisdom - wisdom that you recognized. When you recognized wisdom, it became your wisdom.  You are the source.  If you say to yourself, or others, that your wisdom comes from a holy book, or a great teacher, you miss the point. You have the capacity to recognize wisdom. If you did not, you would not be reading this. Now you must decide whether to trust what you recognize. Will you look outside of yourself to make that decision, or inside?  That is the question.

Rejecting - for any reason - what you recognize to be significant, invalidates your own experience, your own power, and the impulses of your own heart.  Decide for yourself whether what stirs you is worthy of your interest. Look inside yourself. You will find an answer.  If you do not find it immediately, be patient and know that it will come. Your answer may be "Yes," . . ."No," or "Look more closely." It may be specific to your experience. Will you listen to it?  If not, you will always be looking for references, and longing to know from others how they know what they know.