Final answer:
The ego defends itself against the id and superego by employing ego defense mechanisms, which are unconscious behaviors aimed at reducing anxiety.
Step-by-step explanation:
In Freud's theory of personality, to defend itself against the demands of the id and the superego, the ego will institute ego defense mechanisms. These are unconscious protective behaviors that aim to reduce anxiety. The id operates on the "pleasure principle," seeking immediate gratification, while the superego strives for perfection and judges our behavior, leading to feelings of pride or guilt. The ego is the rational part balancing the demands of both id and superego in reality, thus operating on the "reality principle." When faced with conflict, the ego uses various defense mechanisms to distort reality and reduce the anxiety that arises.