Last Updated on June 19, 2019, by eNotes Editorial. Word Count: 340
This is a rather difficult question to answer. Most texts possess themes which speak to the message the author wishes to pass on to the reader. Under these circumstances, most themes exist within a text whose purpose is to challenge the reader to think very specifically about a certain topic in a certain way. Aristotle's On the Soul does not possess openly specific and readily identifiable themes. That said, one can distinguish a couple of themes from the text as a whole.
One theme which could be derived from the text revolves around the idea of seeking knowledge. Aristotle admits that attaining knowledge regarding the soul "is one of the most difficult things in the world." That said, given his text's sole existence revolves around obtaining this specific knowledge, Aristotle continues his search. Therefore, one must only conclude that Aristotle is making a statement that regardless of how difficult something is one should never give up the quest for knowledge.
Another theme which exposes itself over the course of the text is one which addresses wisdom (different than knowledge for these intents and purposes). This reminds me personally of the poem "The Wanderer."
Therefore a man cannot become wise,
before he has earned his share of winters in this world.
According to the poem, wisdom only comes with age. The poem addresses this by stating one only becomes wise when he "has earned his share of winters in this world." One only "earns" winters by aging. With age therefore comes wisdom. Aristotle addresses this idea when he addresses the importance of looking to those who have come before him. Aristotle states that those seeking knowledge must look to their predecessors in order to "profit by whatever is sound in their suggestions and avoid their errors."
Aristotle therefore presents two major (and universal) themes in On the Soul. While Aristotle does not address the themes directly in the text, his message is clear: knowledge and wisdom are the most important when one looks to take on challenging ideologies, like the soul.