Topic vs. Theme

Today's lesson was about themes and the difference between them and topics. A topic was defined as an idea or subject that occurs in the text which covers pretty much anything that the text mentioned. A theme. however, is a particular assertion about that topic, an assertion being a claim which needs evidence to support. A claim without any evidence is useless and just becomes a baseless statement.
Later in class, there were common thematic myths covered. Those thematic myths being:

• There is only one theme for a text when there can actually be many themes (of varying significance)
• A theme is a lesson
• A theme can be a lesson, especially when the target audience is younger.
• More complex texts usually have more complex themes.
• Themes can be one word long.
• That could only be a topic, for example Christmas.

A theme asks, "what ABOUT (topic)?".  Although No Country for Old Men might've been about stealing money that was not the theme. The theme was implied in Joel's line, "The point being that even in the contest between man and steer the issue is not certain."

Personally, I have seen many claim that Quentin Tarantino films have a theme of revenge, but that's just not true, since you can't have a one word theme. You have to ask "what about revenge?".  Is it good? Is it bad? Is it just a thing that happens? Revenge is just the topic of many of his films, although the theme may be regarding something about revenge the theme itself could not be.