Final answer:
The defense mechanism described in the question is projection, where a person attributes their own unconscious feelings or desires to someone else.
Step-by-step explanation:
The defense mechanism described in the question is projection.
Projection is a defense mechanism where a person attributes their own unconscious feelings or desires to someone else. In this case, the young man feels envious of his best friend, but instead of acknowledging his own envy, he projects it onto his friend by believing that his friend is envious of him.
Projection can help the person avoid facing their own uncomfortable emotions and maintain a positive self-image.