I had the honor of asking David Gowler (the Pierce Chair of Religion and the director of the Pierce Program of Religion at Oxford College of Emory University) a few questions regarding the parables and how the modern reader can better understand them.
Enjoy!

What can we in the modern world compare a parable to, if anything?
David: What is parabolic, in many ways, exists in the eyes and/or ears of the beholder. Perhaps if I place the parable into its ancient context, that will help clarify things.

The Greek term for parable (parabolê) typically is used to translate the Hebrew term mashal (plural: meshalim). Mashal is extremely difficult to define, but a central aspect of its meaning is “to represent” or “to be like,” and it refers to a wide range of literary forms that utilize figurative language. The Hebrew Bible tends to use mashal for whatever is “proverb-like,” with hidden or allusive truth, which means that responses of readers or hearers are essential to the process of creating understanding (assuming they understand the analogy being made). Yet the meshalim of the Hebrew Bible do not offer any definitive examples of parables like the ones Jesus created. The Hebrew Bible does contain some fables, such as Jotham’s mashal of the Trees (Judges 9:7–15), Jehoash’s mashal of the Thistle (2 Kings 14:9), and Ezekiel’s mashal of the Vine and the Eagles (Ezekiel 17:3–10), but no Hebrew Bible mashal serves as a direct parallel to the New Testament’s use of parable as a short narrative. Isaiah’s mashal of the Vineyard (Isaiah 5:1–6) might qualify as an allegorizing parable, but of all the meshalim in the Hebrew Bible, the closest we come to a narrative parable is Nathan’s mashal of the Poor Man’s Only Lamb (2 Samuel 12:1–4).

Parables play a prominent role in later Jewish literature, such as in rabbinic traditions, where the rabbis used them for preaching, interpreting Scripture, and providing guidance for daily lives. I like David Stern’s definition of the rabbinic parable as “an allusive narrative told for an ulterior purpose”—usually to praise or disparage a specific situation of the speaker/author and hearer/reader. It draws a series of parallels between the story recounted in the narrative and the “actual situation” to which the parable is directed. These parallels, however, are not drawn explicitly; the audience is left to derive them for themselves, which, again, can be confusing if the analogy/parallel is not clear enough. So the parable is neither a simple tale with a transparent lesson nor an opaque story with a secret message; it is a narrative that actively elicits from its audience the interpretation and application of its message. The social context, then, clarifies the parable by giving the audience the information they need to understand it, and, if the readers do not understand the social context, the parable can also be hard to understand (see the answer to question #3 below).

In Greco-Roman traditions, the parable is similar if not the same as the ancient fable, and rhetorical treatises can help explain what they are and how they work. The mention of Greek fables usually conjures up visions of stories with talking animals that illustrate a simple moral. Yet, in antiquity, the term fable denoted several kinds of brief narratives, but the one that serves as the best example is Aelius Theon’s definition of the fable as “a fictitious story picturing a truth.” The realistic portrayals in Aesop’s fables, for example, are similar to the parables of Jesus. Mary Ann Beavis points out that both are brief narratives that shed light on aspects of human experience and behavior, that usually involve ordinary human characters and situations—like quarreling siblings who are corrected by a loving father—and that, despite their realism, often contain an element of extravagance or surprise. Most fables, like the parables of Jesus, illustrate religious and ethical themes but do not have miraculous interventions (only two of Jesus’ parables have direct supernatural interventions: Luke 12:13–21; 16:19–31). Some fables also include a surprising or ironic element of reversal that is reminiscent of Jesus’ parables.
So, I hope that historical context explains the variety and flexibility of what could be considered a parable today.