There is no one way to identify themes in texts. The following are two of the ways one might use to identify themes.
One might try to see:
Ways in which the main character has changed or what he or she has learned, and the nature of the central conflict.
A Thematic Statement should be expressed as a Declarative Sentence or Sentences. One should be careful to avoid using single statements like “love" or phrases like “Individual vs. Society." These are subjects or topics, not themes. The theme is the author’s idea about the topic. It is useful to identify several subjects introduced by the text and then determine what the author says about this subject.
A theme is a statement about life. When writing a thematic statement one should not mention character(s) in the text by name. The following words are useful when writing thematic statements: people, a person, individuals, an individual or someone.
Warning: A theme should not be so general that it says nothing. For example, the following statement is erroneous because it is so broad it says nothing, “The effects of risk taking can be positive or negative".
Hint: To overcome this, ask the question, “According to the text what are the positive and negative effects of risk taking?" Or ask, “Why is risk taking positive or negative?"
4. All the major details in the story usually relate to the theme and therefore should be mentioned in the thematic statement. Specific details should be listed to support the theme even if they are not part of the theme statement.
5. Avoid absolutes and sweeping statements. Avoid the use of the following words: all, every, always, and never. In other words, never say “never." Instead, try using words and phrases like the following: usually, sometimes, frequently, most of the time, often, hardly ever.
6. The theme should not be reduced to a cliché, a trite, overused saying, such as “Don’t judge a book by its cover."
7. Usually, a well-written text has more than one topic and more than one theme.
8. It is useful to mention the title and author of a text in a theme statement. For example, “In (title), (the author’s full name) develops the idea(s) that…."
St. Rosemary Educational Institution. "Writing a Thematic Statement." http://schoolworkhelper.net/. St. Rosemary Educational Institution, Last Update: 2017. Web. Retrieved on: Sunday 5th March 2017. http://schoolworkhelper.net/writing-a-thematic-statement/.