11.3: Drawing the Line

When there are borderline cases, cases where we can’t be sure whether a word applies to something or not, the word is vague. Vague words are not completely precise. For example, the word ‘bald’ is vague. There are many people who have a bit of hair, and they are not clearly bald or clearly nonbald. Again, some things are clearly red and some are clearly not red, but at the edges (near shades of orange and shades of purple), there are unclear cases.

When we encounter a vague word, there is usually no need to try to make it precise (and in fact any way of doing so would be somewhat arbitrary). Indeed, although precision is often desirable, it is good that many of our words are vague. If we had to learn exactly how many hairs someone needs to be non-bald, or precisely what shades counted as red, we could never learn to use these words. In fact, most of the adjectives (and some of the other words) in our language are vague.

It is not uncommon to hear people argue as follows:

You cannot draw a definite line between X and Y, so there really is no difference between Xs and Ys.

We call this the line-drawing fallacy. There are a great many cases where we cannot draw a definite, non-arbitrary, line between two things, but there are still many clear cases of Xs and Ys (even though there are borderline cases as well).

For example, it is true that we cannot draw a line that neatly separates each person into either the group of people who are for sure bald or else into the group of people who are certainly not bald. There are borderline cases here. But this doesn’t mean that there are not clear cases of bald people (e.g. Patrick Stewart) and clear cases of people who are not bald (e.g., Conan O’Brien). Again, it isn’t possible to draw a precise line between day and night, but it is for sure day at 2:00 P.M. and for sure night at 2:00 A.M.

No one would agonize much over these examples, but there are other cases involving line-drawing that matter more. For example, you probably cannot draw a precise, non-arbitrary line that will separate all weapons into those that should be legal (e.g., hunting rifles) and those that should not be (e.g., nuclear warheads), but this doesn’t mean that there aren’t clear cases of each.

Again, someone might argue that there is no way to draw and line between a fetus that is one day old and a fetus that is nine months old. Indeed, this could be part of an argument against abortion; we can imagine someone urging, “Abortion shouldn’t be allowed, because there is no place where you can draw a line between the fetus being a person and it not being one.” But there are certainly important differences between a very undeveloped fetus and a newborn infant. Often, we can’t draw a precise, non-arbitrary line that separates everything neatly into either Xs or Ys. But that does not mean that there are not many completely clear cases of each. Moreover, it does not follow that just any place we draw the line is as good as any other. Any attempt to distinguish day from night that counts 1:00 P.M. as night is simply wrong.