I always introduce the concept with a simple thought experiment: suppose I bring a tape measure to class, and the day's activity is to determine the tallest student in the room. How might we accomplish that? We talk about precise definitions of "tall," how to minimize errors in measurement, etc., but at the end of that, we understand that we'd take the tape measure, measure each person in class, and the record of inches and feet would settle the matter. The most important part: once our data were collected and properly understood, it would no longer be rational to disagree. You might speak up and say "Well, Brody (or David or Jordan or whoever) might be the tallest to all of you, but not to me! I have my own opinion about who the tallest student in this class is!" But your classmates could demonstrate that you were simply mistaken. Part two of the thought experiment: what if, instead, the day's activity is to determine the most likable student in the class? Not only could we not do that with a tape measure, but no instrument exists that would settle that question. We might each supply an answer and discuss our answers, but it would be entirely acceptable to disagree with the majority: "Bob might be the most likable to you, but I personally find Fred more likable." Nothing wrong with that.
Many times, students' first reaction is to ask, "So it's just opinion?" Then I explain that opinions are things to which reason is entirely irrelevant -- my example generally is the relative tastiness of chocolate versus vanilla -- whereas interpretive theories deal with questions that aren't exhausted by collection and analysis of data, but are proven intersubjectively. People are free to like or dislike any author, according to their taste, but enough people have found Shakespeare's work exceptionally powerful that obviously something exemplary is at work in his writing, even if there's no literary tape measure that can give it an exact weight.
Those are my starter examples. Here are others that I've been collecting:
- An archive versus a memory. Maintaining an archive is an attempt to record objectively demonstrable remnants of past events. On the other hand, memory is a trace of our own subjective experience of those events. And if we compare our memories with other people's, we're likely to find that certain of our stored impressions are widely shared, while others are unique to individuals. But even those, and perhaps especially those, are worth examining: often it's the unique perspective that influences people to think in new and creative ways.
- A health inspector versus a restaurant critic. A health inspector will conduct a thorough examination of a restaurant, checklist and swabs in hand, and will issue a report consisting of data collected through techniques that are standardized and replicable. A restaurant critic will report her subjective judgment of the restaurant's success or failure at delivering an enjoyable eating experience. Parallel concepts are nutrition and flavor.
- Nature versus nurture. Our genes determine certain of our traits, but other traits are our own response to our experience, which is some part happenings in the outside world and some part our own interpretation of those happenings.
- God's sovereignty and faith.
That last one brings me back to where we usually wind up the discussion: the big picture of this duality is that there is a reality out there, a reality outside our skulls that is independent of our observation. Even if we were all struck dead at the same moment, the tallest among us would remain the tallest. But there is also a reality inside our skulls, inside our thoughts, and that reality is not identical for any two people: if every human on earth was struck dead at the same moment, the question of who was the most likable would vanish, because there would no longer remain any sentient people to like, dislike, or behave in a way that was worthy of liking or disliking. And a very simple, straightforward definition of God can be derived from this: God is the one for whom the outer and inner reality are unbroken, continuous.
If you've got any other good illustrations of the gap between that which is demonstrated objectively, and that which is argued with intersubjective accounts of experience, I'd love to pile up a few more. It's a powerful idea, and the more illustrations I've got to bolster it, the better we do.