Earlier quoted context omitted.
The lowercase phi (φ) is the accepted standard denotation for the golden ratio.
ok, but how do we know that the golden ratio is the optimal ratio for lines of text?
To my eye, Golden Ratio Typography seems to hit the sweet spot.
In a future article, I'm going to talk about the notions of a "sweet spot" and a "good eye for design" and show how these concepts point to the existence of universal subjective preferences.