Thought about people around you convinces you who and what they are. But the identification of thought with your existence here must be temporary for every thought you thought limits the essence of a thought...
The essence of a thought is formless. Words describe what is thought through sense perception from the outer reality. ( Example: She is deceiving, a liar, pretender, not even a trusting person. He is not good, fool, boast, liar etc. ) So, in general, you created the thought that you cannot trust, can't rely, can't believe anybody. However, those are merely ACTS of friends identified with your thoughts. Thought like this is dangerous because it creates doubt, reservation, unlikely situation to all the people you will be encountered. But, this happens that's very true because most of the "people don't know who they are." ( Echart Tolle ) So, mind creates a thought about people around. Thus, this kind of thought would grow and it becomes your belief once you, yourself, become identified with it.