Diana Raffman

Professor Diana RaffmanOut of the Blue

U of T Mississauga Philosophy prof may have provided the perfect solution to previously unsolved, Ancient Greek paradox

What do words like “tall” or “old” or even “green” and “blue” have in common? They all fall into a category of vague words that cause much debate among philosophers, linguists and other interested parties, according to Professor Diana Raffman (pictured) from U of T Mississauga’s Department of Philosophy.

“We all have an intuitive sense of what vagueness is – it refers to any unclarity in our speech” said Raffman in opening remarks for a lecture held in her honour on January 27, recognizing her exceptional scholarly achievements as a recipient of the 2015 Research Excellence Award, which is given annually at UTM.  

"But I think the best definition of linguistic vagueness is that it’s the property of possessing blurred or fuzzy boundaries of application.” Prime examples of vague words are ‘old,’ ‘adult,’ ‘juvenile,’ and color words like ‘blue’ and ‘green:’ there is no clear boundary between people who are old and people who are middle-aged, or between adults and juveniles, or between blue and green.

Raffman went on to thoughtfully outline her approach for tackling the vagueness of language in her research, the inherent problems that arise as a result of this lack of clarity, and why we should care about vagueness.

Raffman explained that one of the most notorious problems caused by linguistic vagueness is the sorites paradox, an Ancient Greek puzzle from 200 B.C. that remains unsolved despite many efforts to do so. The puzzle is generated by “slippery-slope reasoning” whereby one step down the slope forces you to make all subsequent steps, landing you in an absurd conclusion.  For example, consider a series of people progressing from an adult aged 35 to a juvenile aged 14, where each person’s age is one day younger than the last. Since an interval of one day can never change an adult into a juvenile, or more generally change an adult into a non-adult, it looks as if we are forced to say that all of these people are adults; if two people differ in age by a single day, then if one of them is an adult, so is the other.  (What causes this strange result is the so-called tolerance of the vague word ‘adult;’ it tolerates small differences in age.)  However, we know that not all of these people are adults; in particular, a 14-year-old is not an adult, says Raffman.

She argues that the paradox can be solved by understanding certain features of our use of vague words. To show this, she presented the results of an experiment she ran with two psychologist collaborators from Ohio State University. Subjects were shown a series of coloured patches progressing from a clear blue to a clear green. They had to classify each patch either as blue, or as green, or as a borderline case. In these classifications, Raffman and her colleagues found a pattern called hysteresis, where a system tends to remain in a certain state once it’s gone into that state. When subjects were shown the colored patches one at a time, immediately after they shifted from saying ‘blue’ to saying ‘green,’ they were shown the preceding patch they had just classified as blue. Now, they classified that preceding patch also as green, even though they had classified it as blue just a few seconds before. This pattern is hysteretic.

According to Raffman, the hysteresis makes it possible for us to stop saying ‘blue’ (or 'adult') and start saying ‘green’ (or 'juvenile') without imposing an unjustified boundary between the two categories; hysteresis smoothes out the shift from blue to green (or from adult to juvenile). This feature of vague words “allows us to talk about the world around us, which changes continuously,” stated Raffman.  And in other words, she explains, the hysteresis enables us to stop sliding down the slippery slope.

These findings outlining the evidence of hysteresis and tolerance culminate with Raffman’s proposal of a solution to the sorites paradox, “I have now proposed a solution [to the sorites paradox] which—after I’m dead, no doubt—will enjoy widespread acceptance,” joked Raffman.

The most significant instance where vagueness becomes problematic, and where we should care about it, she claims, is in the law. She cited numerous examples where the vagueness of words has fueled debate, such as in the abortion controversy about when personhood begins, or regarding the question of when a person’s IQ is high enough to make him eligible for execution (this question arose recently in a U.S. Supreme Court case), or in cases where the vague boundary between being an adult and being a juvenile makes the appropriate sentence for a crime unclear.

The lecture concluded with a flurry of questions that came up surrounding other vague words and instances, and Raffman was happy to continue the discussion.  She called vagueness a “pressing matter to anyone who likes to think deeply about things.” And it’s clear she has thought and probed deeply about vagueness in language.

The host for the Research Excellence Lecture Professor Bryan Stewart was thrilled with the turnout, the engaged audience, which consisted of staff, faculty and students from a diverse mix of departments at UTM including the library, Anthropology, Biology, Chemical & Physical Sciences, Math & Computational Sciences, Philosophy, Psychology, and Sociology, and the outstanding caliber of the lecture. “This captures exactly what I envisioned for this event, and a prime example of what the annual Research Excellence Lecture should be,” said Stewart.


If you know an outstanding researcher, consider putting them forward for a Research Excellence Award, which is given annually to exceptional UTM researchers.

By Carla DeMarco