Chapter 14 focuses on what factors influences our personalities and behaviors. Studies on twins and adoption cases suggest that many personality traits are hereditary but that doesn't mean that environmental roles don't play a factor increasing the nature vs. nurture debate. Sigmund Freud's lasting impression on psychology is based on the principles on psychic determination, symbolic determination, and unconscious motivation that is still widely controversial today. Critics of his psychoanalytic theory question the lack of evidence, lack of falsifiability, and failed predictions among other things. However, Freud's legacy with the unconscious is one of the most known theories.
In addition, there are also behavioral and social learning theories of personality. Behaviorists believe in the unconscious processing but deny the existence of the unconscious. They believe that genetics and the environment determine personality. Social learners believe the central role of thinking determines personality.
So like with many things in psychology, there is not one cutthroat answer to what determines personality. It is a combination of many factors that establishes who we are which ultimately adds to the uniqueness of every individual. So, be you because no one else can do it better!