Posts Tagged ‘optics’

In discussing Roger Bacon, I casually mentioned that he was the contemporary of Robert Grosseteste, as if that were a name everyone should recognize. Maybe it is, but in case you don’t, here’s the scoop.

Grosseteste lived from 1175 to 1253, entirely overlapping the life of St. Francis, whose Friars he taught at Oxford; remember, Roger Bacon was a Franciscan; he may or may not have actually met Grosseteste. He was also Bishop of Lincoln for the last 20 years of his life.

What else?

Well, it is interesting to note and he wrote an allegory about redemption called the Castle of Love. In his story, a king has four daughters, mercy, justice, truth, and peace, and they argue about the rightful fate of a guilty vassal. It’s an interesting approach to the doctrine of the atonement, and the fact that he wrote it is a measure of his desire to preach the gospel persuasively.

He was a good bishop.

He was a good statesman, which was part of the job of being a bishop in those days.

He was also an important philosopher, one who influenced Roger Bacon. Between 1230 and 1235, he wrote commentaries on Aristotle for his students, and one important aspect of this is that he certainly understood the dual path of scientific reasoning:

  1. One generalizes from observations and comes to a conclusion about universal principles.
  2. From that universal conclusion, one lays out what to expect in terms of observation and then checks whether new observations further affirm the universal principle or require its correction.

In other words, science requires both inductive reasoning, which goes from many observations to a single principle, and deductive reasoning, which goes from an abstract principle to the interpretation of many individual facts. He called inductive reasoning “resolution” since it brings many things into focus; he called deductive reasoning “composition” because it suggests how to place other physical events under the umbrella of a principle. Science consists of resolution and composition.

Seems obvious, but lesser men emphasize one path at the expense of the other. His ideas formed a tradition of placing science firmly in the realm of observation and experimental verification, and Galileo specifically built upon that tradition almost 400 years later.

Geometry and Optics

It is really impossible to think of studying optics without a knowledge of geometry. What is reflection if not geometry? Light strikes a flat surface, and the angle at which it falls is the same as the angle at which it bounces away: “the angle of incidence is equal to the angle of reflection.” Grosseteste wrote about optics and about the importance of math for good science.

He also wrote thoughtfully about the rainbow, although I don’t know exactly what he said because what I found about this quickly turned to a discussion of Roger Bacon’s development of his ideas. Nevertheless, he does seem to have understood the exciting possibilities opened up by an understanding of the principles of light:

“This part of optics, when well understood, shows us how we may make things a very long distance off appear as if placed very close, and large near things appear very small, and how we may make small things placed at a distance appear any size we want, so that it may be possible for us to read the smallest letters at incredible distances, or to count sand, or seed, or any sort of minute objects.”

In other words, he envisioned the twin invention of the telescope and microscope, still 350 years in the future.

When you notice how others have a habit of portraying the progress of scientific thought as a mental jump from the Greeks of 300 BC to the Renaissance of 1500 AD, think of Grosseteste. The medieval thinkers brought Greek thought into the Christian intellectual world, reflected on it, gave it a proper home, and developed it. They disagreed with Aristotle on some issues, but they thought about his ideas.

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