If you have been using farther and further interchangeably, don’t start beating yourself with a hose. In general usage, you aren’t wrong.
Garner tells us that
“Both are comparative degrees of far, but they have undergone DIFFERENTIATION. In the best usage, farther refers to physical distances, further to figurative distances.” *
What that means is that over time, given the development of the English language, these two words have emerged from having the same meaning to a state where one refers to physical, measurable distance (farther) and the other (further) has been relegated to describing a more cerebral distance, as in “after further investigation….”
It’s one of those differentiations that doesn’t amount to a hill of beans in general usage, but is helpful if you want to be technically correct. If you are writing a piece, for instance, it’s helpful to be technically correct. People who know the difference are thrown by incorrect usage, and it can set up a mindset which is distracting if the “wrong” word is used. But in spoken language, it really doesn’t matter enough to worry about it.
If you want to describe the length of a base hit in baseball, for instance, it is appropriate to say that “Pedroia’s punch to near left field was farther than his last attempt, when the hard-hit ball was snagged by the shortstop.” The sentence indicates that the length of the single was measurable in feet or yards.
But it is also appropriate to say, “Pedroia’s single moved the Red Sox further along in overcoming the Yankees in this hard-fought game.” The comment is about perceived advancement rather than measured distance.
It’s easy to get all bent out of shape over such distinctions, which only destroys the pleasure of using language. The main point of it all is communication. If the words are switched or “confused” it doesn’t stop the speaker or writer from making the point. The reader or listener gets the point and moves on through the dialogue. To stop the speaker and correct (him) is to destroy the moment of communication. Nobody is more guilty of this than I am. I revel at times in “correcting” someone’s use of language, probably to gain power over them by demonstrating a small, insignificant piece of knowledge that only serves to embarrass them and destroy the conversation momentarily. Shame on me.
Photo Credit: Zadar, Croatia
* Bryan Garner, Garner’s Modern American Usage, p. 346)