No, it is unethical to use another author's ideas without crediting his or her work or literature. Failing to credit an author's work in your own work is known as plagiarism. Plagiarism has serious and sometimes even legal consequences in both educational institutions and beyond that in the corporate world and publishing industries. To avoid plagiarism and remain ethical it is best to quote ideas given by another author and clearly state the source from which you are quoting the author's work.
They used their way with words to become successful in journalism and other political and religious ways. They contributed to our culture and taught us many different was to grow potato crops and ways to make different foods. We became very culturally diverse.
The answer to this question is the term introspection. Introspection is the observation and interpretation of a persons own feelings, thoughts, sensations, and images. It is an observation of the mental and emotional state of a person by examining his or her soul.