In literature many of man's deepest philosophical questions can be asked in different and creative ways compared to a normal philosophical treatise. These questions such as, "Why are we here?", "What is the meaning of life?" or "What is love?" have been pondered ever since man was capable of critical thought. In literature these questions and other fundamental truths can be explored through the medium of the narrative in a way that will help readers broaden their philosophical horizons and come to a conclusion or in some cases have more refined questions to replace their previous questions.
Examples include the exiled Portuguese Jew Baruch Spinoza in the 17th century who wrote an elegiac poem that questioned the nature of his despair in a philosophical way and he also meditated on both the nature of life and the nature of death. Other themes in his writing are whether God has a grand plan for us, what it is and how will we know what it is? Friedrich Nietzsche, the German philosopher, was also known for expressing his ideas in literature, for example in Thus Spoke Zarathustra, which is an account of Zoroaster's teachings.
One of literature's favorite topics is love, the nature of love and beauty and it is no surprise that philosophers use literature to explore this area. Nietzsche wrote about this as well in "Beautiful and Ugly" from Skirmishes in a War with the Age in The Twilight of the Idols and his ideas are beautiful and profound as to the nature of love and beauty. Plato also explored this area in Symposium where he talks about beauty and how the lover perceives the beauty of the person who has his affection.
Another of the questions that literature tries to make sense of is the nature of good that can only really be described as the opposite of evil, and the fact that our existence is based on us being cruel and murdering other things to eat or wear. Philosophy tries to answer these questions and literature is used to try and make sense of it and try and provide different perspectives and situations to describe the nature of evil. The first group of people to try and make sense of the nature of evil in literature were the ancient Israelites who in their psalms accepted that God created everything and therefore also created evil, meaning that it is part of God's plan and must be accepted. This is seen especially in the book of Job where the title character is punished seemingly on God's whim after a dare from the Satan.
Other writers also try to make sense of this issue including Lord Byron whose character Cain sums up the question most eloquently by asking: "Because God is all-powerful, must he be all-good? And if he is all-good, why then is evil?". This question is even addressed in a famous children's poem Tiger, Tiger by William Blake who wrote of the tiger, "Did he smile his work to see?/Did he who made the Lamb make thee?" -- trying to get at the problem of evil within nature and the chain of cruelty that makes up the food chain, with the tiger hunting the lamb, but itself being hunted by humans.
Another topic that man dwells upon is the nature of time in the universe. In all languages there are many words for time -- for example, today, tomorrow, yesterday, minute, hour, second, week -- and therefore it is no surprise that literature is used as a medium for tackling the subject and fairy tales are known to start with the phrase "once upon a time." Probably the best example is the tale of the sleeping beauty who is preserved until woken by a kiss, but also woken to a world where she will die. As the reader gets older the message in the book about time changes, and from the fairy tales, where time is nothing and there is no change, to books read in adulthood, where the philosophical questions revert to what to do with the time, we have and the nature of change. Pierre de Ronsard probably says it best in his poem The Paradox of Time: "Alas, Time stays,--we go!". Thomas Mann in The Magic Mountain writes about the nature of time, space and motion in a most beautiful way.