For out of olde feldes, as men seyth, Cometh al this newe corn from yer to yere

Chaucer, of course. Beautiful. Used as a chapter heading by C. S. Lewis in his The Discarded Image; you should read it. But it turns out that a fuller quote (from the prologue to the Parliament of Fowls) is

For out of olde feldes, as men seyth,
Cometh al this newe corn from yer to yere;
And out of olde bokes, in good feyth,
Cometh al this newe science that men lere. 

And that isn't so good. For those with poor early-English skilz, that is:

For out of old fields, as old wives say,
Comes the new corn from year to year,
Just so do old books, seen with new eyes
yield all that is new, that we call Science.

And that I gather was indeed how they thought in those days: the old ways are the best. It's all very Platonic. Nowadays, we regard science as grounded in experiment. Unless you're a string theorist, of course. Wiki provides a dream-like summary, which suggests PoF is about the importance of freedom of will, which would be good. Maybe I'll read it some time. But that brings me to the start of Pof:

The lyf so short, the craft so longe to lerne.
Th’ assay so hard, so sharp the conquerynge,
The dredful joye, alwey that slit so yerne;
Al this mene I be love.

That too is hard, but I'm going to leave it untranslated (there's a version here if you like). The last line tells us it is about love, but it doesn't have to be.

Refs

* Life is short, and Art long; the crisis fleeting; experience perilous, and decision difficult.
Aphorisms by Hippocrates; from ThingFinder.
* The life so short, the craft so long to learn; from ThingFinder.