Sunday, April 10, 2011

The Parabolic Jesus

This past weekend, I attended a conference on the future of Unitarian Universalism in which a minister referred to Sallie McFague's Metaphorical Theology. I don't know much about theology myself, so I was paying only partial attention when I heard the phrase "the parabolic Jesus." My ears perked up.

I'm a physicist. I hear the word "parabolic" more often than the average person, and to me it means something in the shape of a parabola, which some may remember from second-year algebra. A parabola is a conic section, the locus of points equidistant from a point and a line, equivalent to an ellipse in which one of the foci is at infinity.

I thought it was far more likely that the word was supposed to refer to "parable," or a Jesus who taught by means of storytelling. But it didn't seem to me that "parabolic" could derive from the word "parable." (Where does the "o" come from?) I spoke to the presenter afterward and she confirmed that she had, indeed, said "parabolic."

It turns out that "parabolic" really is the adjectival form of "parable," and that this definition even appears first in a dictionary. From Merriam-Webster:

Definition of PARABOLIC

1: expressed by or being a parable : allegorical
2: of, having the form of, or relating to a parabola <parabolic curve>

So I guess the mystery is solved.
But while the first definition is clearly the one that applies to the concept of a "parabolic Jesus," the images that immediately entered my mind using the second definition were interesting. A parabolic mirror reflects parallel waves from infinity into a single focal point (this is why satellite dishes, for example, are paraboloids) and so I was thinking of a parabolic Jesus as somehow being able to focus diverse lifestyles and philosophies into a single common goal of justice---not too far off from Unitarian Universalism, sometimes described as the religion of Jesus rather than the religion about Jesus. Metaphor, indeed!

1 comment:

firezdog said...

Apparently both words have the same root, the Greek PARABOLE which refers to throwing besides or something thrown besides (PARA + BALLEIN = BESIDE + THROW). So in the context of language, a parable involves a comparison -- in the math context, I'm not so sure. (Could it have something to do with the shape of projectile motion? But I suppose the word is older than that.) Very interesting!

Also I find this description -- "the locus of points equidistant from a point and a line" -- a bit unclear. What is a locus of points? Is the point they are equidistant from on the line? Is that the line that goes through the "center" of the parabola?

Also, what do you mean "a parabolic mirror reflects parallel waves from infinity into a single focal point"? I suppose one would need a picture. But I imagine two sine curves in the same phase occupying different parts of a plane as parallel waves. But what does it mean to reflect a sine curve to a point? Would there be any symmetry in the reflection? (If you reflect a rectangle across a line, you get another rectangle on the other side -- but what could it mean to reflect a rectangle into a point?)