Classically, vagueness has been considered something bad. It leads to the Sorites paradox, borderline cases, and the (apparent) violation of the logical principle of bivalence. Nevertheless, there have always been scholars claiming that vagueness is also valuable. Many have pointed out that we could not communicate as successfully or efficiently as we do if we would not use vague language. Indeed, we often use vague terms when we could have used more precise ones instead. Many scholars (implicitly or explicitly) assume that we do so because their vagueness has a positive function. But how and in what sense can vagueness be said to have a function or value? This paper is an attempt to give an answer to this question. After clarifying the concepts of vagueness and value, it examines nine arguments for the value of vagueness, which have been discussed in the literature. The (negative) result of this examination is, however, that there is not much reason to believe that vagueness has a value or positive function at all because none of the arguments is conclusive. A tenth argument that has not been discussed so far seems most promising but rests on a solely strategic notion of function.

2.1 What is vagueness?

Vagueness is usually explained by reference to paradigmatically vague terms such as "blue", "tall", or "heap". Moreover, three characteristics have been accepted in the literature as essential to vagueness. According to Rosanna Keefe (2000, pp. 6–7), vague expressions are commonly understood to: 1) admit borderline cases, 2) be susceptible to the Sorites paradox, and 3) (apparently) lack sharp boundaries. These three criteria are, however, rarely accepted as individually necessary and collectively sufficient conditions for vagueness. Sometimes they are treated simply as symptoms or signs of vagueness.

Although it is controversial what properties are essential to vagueness, we could surely say that vagueness has a positive function if at least one of the three characteristics has a positive function. If it can be shown that being susceptible to the Sorites paradox, lacking sharp boundaries, or admitting borderline cases has positive effects, then we can also justifiably say that vagueness has a value. Maybe vagueness has a value only if all three properties are combined or due to some other property of vague terms that is (more fundamentally) connected to vagueness. We will look at this possibility when examining the arguments in due course. What is certain, however, is that it is not enough to show only that sometimes we prefer vague terms when we could have used more precise ones instead; we need to show that we do so because of their vagueness (however understood).

2.2 Value, function, utility

But what can it mean that vagueness has a positive value, function, or use? People who have claimed that vagueness has a value have rarely explicated what having a value means or even in what sense vagueness might possibly have a value.

Clearly, when asking what value vagueness might have, we are concerned with instrumental value. The instrumental value of something is the value that it has in virtue of the fact that it is a means to something desirable. Desirability can be understood very broadly as anything that is desired by someone. If Mary desires to manipulate her audience into believing that she is a goddess, then whatever is a means to fulfilling that desire has instrumental value to her. Usually, desirability is understood somewhat narrower: more normatively. Something has instrumental value only if it is a means to the common good, to some rational goal, or to something that is objectively desirable.5

We have an intuitively clear grasp on what it would mean for tools such as pens to be instrumentally valuable. A pen has instrumental value if it helps us to accomplish tasks such as writing or drawing. We desire to write a letter, and the pen is a suitable means to that end. This is due to some properties such as, for example, its handiness or having a functioning ballpoint, but not due to others such as, for example, its having a certain colour.

A pen might even be valuable as a hair clip or a tool for scratching. Again, this is arguably more due to its handiness and less due to its colour. It is indispensable that the pen has some colour, but this does not make the colour a means to the end of pinning up one's hair. In contrast, a pen can have aesthetic value, too. With regard to this end, its colour may very well be the property that is functional to further it. Its colour may help to accomplish that we feel pleased when looking at the pen.

How are things when examining the potential value of vagueness? How can borderline cases, Sorites susceptibility, or the lack of boundaries be useful? What might these properties help to accomplish?

Please note that it does not suffice to have an explanation for why there is vagueness in our language. Of course, we also want to know why we speak vague languages. But giving such an explanation is not the same as providing reasons for the claim that vagueness has a value. Equating this presupposes an impoverished (and fairly uninteresting) concept of value. We would not say that something is valuable if it is an unavoidable side effect of something that has a value. Something has a value if it helps us to achieve something.

Of course, there are also people who claim that some linguistic property that they call "vagueness" has value. In most cases, it becomes immediately clear that these people do not mean vagueness in the sense captured by Keefe's three characteristics when they argue for the "value of vagueness" — but some other property of (contingently) vague expressions (such as their generality or ambiguity).6 Other people, however, list paradigmatic examples of vague terms, use Keefe's three characteristics of vagueness, and cite the philosophical literature on the Sorites paradox and borderline cases. These people claim that vagueness in the philosophical sense has a positive function. In what follows, I will examine arguments for this claim only.

• (1) X is desirable.
• (2) Vagueness is a suitable (or indispensable) causal means to bring about X.
• (3) If vagueness is a suitable (or indispensable) causal means to bring about something desirable, then vagueness has instrumental value.
• (4) Thus: Vagueness has instrumental value.

3.1 The argument from communicative success

Some philosophers have argued that vagueness does not preclude successful communication and thus cannot be problematic.7 They reject the Fregean ideal of a perfect, precise, and unambiguous language. As Wright (1975, p. 325) puts it, "we have long since abandoned the Frege-Russell view of the matter. We no longer see the vagueness of ordinary language as a defect." Indeed, there are hardly any philosophers who defend this ideal anymore. Most linguists and philosophers of language today explicitly hold the view that ordinary language is fine as it is. It is close to uncontroversial that vagueness is not necessarily a problem. But what does this tell us about its value?

The most famous version of the argument from communicative success might be attributed to Rohit Parikh.8 Parikh (1994) game-theoretically shows that even if borderline cases actually arise and unclarity results, as long as the conversational purpose is not (seriously) obstructed, vague messages can be useful. According to his interpretation of vagueness, vague terms have an extension which is slightly different for different language users such that there is disagreement between them in some cases (sc. borderline cases). Based on this understanding of vagueness, he shows that vague messages can succeed in promoting the conversation's goal — even under perfect alignment of interests.

Consider the following situation: Ann wants Bob to bring her the topology book from the library. She only tells him that it is blue. Due to its vagueness, the phrase "blue books" does not have a single extension, but is divided into blue_A books (within Ann's semantic) and blue_B books (within Bob's semantic); the extensions of the homonymous terms "blue_A books" and "blue_B books" merely overlap. As long they do so sufficiently (i.e., if there are not too many borderline cases), Bob obtains sufficiently useful information to efficiently find the correct book and bring it to Ann. If Bob searches all blue_B books first and then the others (the less and less blue ones from his perspective), he will find the correct book with higher probability more quickly than if he has to search all books more or less randomly. Bob will thus save time by searching all blue_B books, even though this is not (strictly speaking) what Ann intended.

Parikh's representation captures an important aspect of vagueness. What is problematic about it, however, is that language users usually do not unconsciously have idiosyncratic idioms which they assume to be precise. It is possible for language users to explicitly disagree in borderline cases on whether the term correctly applies or to explicitly agree that they face a borderline case in which they should suspend their judgement about the term's application. Vagueness does not (merely) consist in incompletely overlapping extensions between idiolects. But if we accept that this captures at least an important aspect of vagueness (and I think that we should), we can conclude with Parikh that this property of vague terms is useful inasmuch as it does not preclude successful communication.

Do we also have an appropriate argument to show that vagueness has a value? Parikh's argument establishes the claim that borderline cases do not preclude successful communication. It does not establish, however, the claim that borderline cases are a suitable causal means to bring about successful communication. Parikh convincingly shows that communication in vague terms can be valuable in the sense that it is better than no communication at all. However, it is also clearly the case that Ann and Bob would communicate even better if the extensions of blue_A books and blue_B books would overlap entirely, that is, if the terms used were precise.9 Parikh presupposes that vagueness is a necessary feature of natural language, which it arguably is, and, based on this presupposition, argues that natural language can be used to successfully exchange information despite its vagueness. Parikh cannot — and does not even try to — explain why vagueness is valuable in a more interesting sense. Unless we are willing to say that something is valuable if it does not preclude something valuable, we cannot draw the conclusion that vagueness is valuable.

This is also the case for more elaborated scenarios like the ones discussed by van Deemter (2009, pp. 624ff.). He argues that the vagueness of vague terms facilitates search. Van Deemter asks us to imagine a situation in which a diamond has been stolen from an emperor by one of his 1,000 eunuchs, and the only witness can describe the thief just with the expression "tall". Due to its vagueness, van Deemter argues, the emperor can rank the eunuchs, searching them from tallest to less tall, and thus save time (instead of searching all the eunuchs randomly). I take it that, also in such scenarios, communication would be even more successful if the terms used would be precise (and that the vagueness here is practically unavoidable due to limited information). But even if that was not the case, the property facilitating search is not borderline cases, Sorites susceptibility, or boundarylessness. Van Deemter even mentions himself that it is the gradability of the term "tall" that is needed to make sense to rank the eunuchs in the first place. But gradability is not the same as vagueness. We can imagine a term "tall*" that is gradable and allows for ranking eunuchs from tallest* to least tall* but does not allow for borderline cases, is not susceptible to the Sorites, or has precise boundaries (by, for instance, introducing a sharp cut-off point at the 500th eunuch that is precisely 170 cm tall).

As Charles Peirce is supposed to have said, "vagueness is no more to be done away with in the world of logic than friction in mechanics."11 Accordingly, the purpose of most conversations can be furthered by using vague terms. Conversations demand different "ideals of exactness" depending on their purpose. What counts as perfectly precise in one conversation, is unacceptably vague in another.

Just as with Parikh's claim about communicating successfully with vague language, there is nothing to say against this claim. It is as convincing as modest. Communication would obviously be hindered by always telling the time exactly to the nanosecond. Doing it would achieve nothing. Indeed, it would violate the conversational maxims of quantity and relation to always telling the time exactly to the nanosecond or to describe the blueness of a book in terms of its wavelength. Even though a message informing about the exact time would be more precise, it would also be more informative than required and, as a result, less relevant for the purposes of the conversation. There are some contexts in which the highest possible precision is pursued, as in science or logic. But the standard of precision is adjustable. It depends on the object and purpose of the conversation. As such, in virtually all contexts of ordinary conversation it is significantly lower. More importantly, the fact that we usually do not — and should not — tell the time to the nanosecond or describe colours by their wavelength spectrum does not entail that there is value in the vagueness of vague language.

3.2 The argument from stability

Some have seen in an argument by Manfred Pinkal (1995) evidence for the claim that vagueness is valuable. He argues that a coarse-grained degree of granularity can facilitate stability in judgement. Perhaps this means that also vagueness (due to the fuzziness in the terms' extension and the lack of (sharp) boundaries) can facilitate stability in judgement. Let us have a look at his argument and the concept of granularity.

Granularity is the concept of breaking down a description into smaller parts (or granules). A coarse-grained description contains only a few parts and is thus less informative than a more fine-grained one. For instance, one can describe someone by saying that she is a person (coarse-grained description) or by saying that she is a self-confident, 190-cm tall, and brown-haired Polish citizen (more fine-grained description). Most parts in the descriptions can be decomposed further into finer levels of granularity, for example, that the person's hair is long, thick, and parted on the left.

Now, if we were to describe someone by her precise height measured to the tenth decimal place, the description would need to be adjusted on a regular basis. The same is true if we describe her by the number of hairs on her head. Otherwise, it would not fit the subject who is slightly changing in height and number of hairs every day. Because we cannot simply perceive the height of a person or the number of hairs exactly how they are, it is better to be less precise.

Consider the following two utterances:

We can now try to explicate the argument from stability:

However, generality must be differentiated from vagueness, as pointed out in section 2.2. A higher generality entails that the utterance is true in more (possible) states of affairs. The utterances in (E1), (E2), and (E3) will all be accepted as true (or appropriate) if Anna has a height of 191.02 cm. The utterances in (E1) and (E2) will, however, also be accepted as true (or appropriate) if Anna has a height of 190.98 cm. In contrast, if the speaker utters (E3), she can be reasonably criticized if Anna's height differs even by a millimetre from 191.02 cm. The lack of (sharp) boundaries is not what makes such less than fully precise utterances useful. It is their generality. Thus, Pinkal does not establish anything about the value of vagueness when he argues that sometimes a more coarse-grained degree of granularity is useful. He establishes that generality can be valuable.

3.3 The argument from perception

There seems to be an ambiguity and confusion about the term "fuzziness". Vagueness concerns fuzziness in the extension of the term "rain"; it does not concern the fuzziness Waismann and Wittgenstein talk about. The phenomenon that we perceive may more or less clearly qualify as rain, but this does not depend on any fuzziness in our perception. It depends on the fuzziness in the term's extension — on there being borderline cases and maybe on the boundarylessness and Sorites susceptibility of the term. Evidently, borderline cases, boundarylessness, and Sorites susceptibility can be there when perception is rather exact; we can count the number of sand grains; and we may even know everything there is to know about a particular arrangement of grains and it might still turn out to be a borderline case of "heap."16 Conversely, our perception can be blurred, while at the same time the term clearly applies to the phenomenon experienced — something that quite generally is the case when we use terms such as "rain" to clearly refer to the rainfall that we perceive more or less blurredly.

3.4 The argument from memory

It seems that two cognitive mechanisms described by Alan Baddeley (2007) support van Deemter's conclusion. First, there is semantic coding by which only the meaning of an expression is retained, whereas the expression itself is forgotten. Second, there is chunking by which a handful of items are clustered together as a unit. Chunking is clearly connected to generality. We lump together specific information into general "chunks." This is perhaps what is also going on in the case of perception. If details are corrupted or lost, one can choose a more general expression instead of a more specific one. Even if you cannot remember whether there are hundreds or merely tens of thousands people, you are usually still able to say whether there are more than 1,000 (or more than 10,000, etc.).

Semantic coding, however, could be the source of vagueness. Maybe we really think "vaguely." Maybe, it is easier for our memory to retain a fuzzy image than a clear-cut one. Let us assume for the sake of the argument that this is the case. Then we can explicate the argument from memory:

However, it is not enough that the vagueness of vague terms is a necessary consequence of their other (actually valuable) properties for it to be valuable. As Hrafn Asgeirsson (2015, p. 426) argued, "value only ‘transmits’ from ends to means but not to necessary consequences of those means." That is, whereas semantic coding facilitated by a vague and general term may be valuable in virtue of being a means to effectively memorize and remember information, its vagueness (even though it might be a necessary consequence of semantic coding) is not. The argument goes through only if we assume an extremely diminished sense of value because only then premise (4) can be upheld.

3.5 The argument from metaphysics

Something very similar can be said for another argument that might be made for the value of vagueness. Because the world is fuzzy and we want to correctly and adequately represent the world, we should use vague language.

A term such as "mountain" is vague because it is susceptible to the Sorites paradox and there are (possible) borderline cases of mountains. It, so to speak, fuzzily refers to some objects. The term can, however, also be used to (clearly) refer to fuzzy things in the world. When referring to the mountain Zugspitze with the phrase "this mountain", we do not care whether the mountain begins at the camp at an altitude of 1,000 meter, at the tree line at 2,000 meter, or anywhere in between. But this fuzziness in the objects themselves has nothing to do with the fact that there are borderline cases of mountains in the world.

In order to maintain premise (3), one would have to say that the world is fuzzy not because there are fuzzy objects in it, but because there are things in it that we fuzzily refer to with our vague language. Then, however, the argument begs the question because the world cannot be considered fuzzy without reference to our already existing vague concepts: Vague concepts are needed to correctly and adequately represent a world that is fuzzily divided by these concepts.

3.6 The argument from learning

Some philosophers have hinted at the possibility that vagueness could improve the learning of language. Maybe it is easier to learn vague terms than to learn precise ones? In fact, children first learn vague expressions and only later more difficult precise ones such as number words and mathematical operators. In general, children learn expressions by reference to prototypes.18 They learn the expression "red" by reference to fire trucks, roses, and sunsets. They do not care about boundaries between red things and non-red things.

Nora Kluck (2014) claims that vagueness plays the central role in the learning strategy of overgeneralization. Consider a child who does not yet know the correct expression for some object. She could either remain silent, thus giving away even the chance to be understood; or, alternatively, she could overgeneralize making herself at least potentially understood. Kluck claims that vagueness facilitates overgeneralization because it allows the child to freely move within the borderline area. She can use a term that only borderline applies if she does not know a better term which would clearly apply. Thus, she argues, overgeneralization is a communicative strategy in language learning relying on the use of vagueness. And this means that vagueness has a value. Let us explicate the argument from learning in this way:

More strikingly, the value of overgeneralization is highest when the child's audience can figure out that she wanted to clearly apply the expression — despite it semantically not clearly or even clearly not applying. Borderline cases here are least disadvantageous when their main effect is mitigated; they are not disadvantageous when we can figure out that the term is intended to apply even though it is in fact (semantically) a borderline case. Hence, also the argument from learning fails to show that vagueness has instrumental value.

3.7 The argument from cognitive costs

Maybe overgeneralization does not require vagueness but somehow vagueness makes our language processing easier, does it not? There is reason to believe that vague messages can be processed more easily than precise ones and, for that reason, cause less cognitive costs. It is arguably easier to pronounce the term "many people" than "324,542 people." It is arguably also easier to hold the thought in mind and to learn the term. Examples such as this one are often used in an attempt to demonstrate that vagueness is valuable because it makes it easier for us to use language. Let us explicate the argument from cognitive costs as follows:

It appears that we generally use language according to some form of the mini-max principle, that is, we are as unclear and inarticulate as possible in order not to waste energy, while at the same time as clear and articulate as necessary in order to still get the message across. Hence, the goal of avoiding unclarity has to be balanced with the goal of not wasting energy. This principle is a reformulation of the so-called false Zipf's law.19 If that is true, any formal proof for the value of vagueness based on cognitive costs becomes trivial. The agents' expected utility increases simply because costs decrease.20

As Manfred Krifka (2009) points out, it is often beneficial for both speaker and listener to use descriptions of the world at a more coarse-grained degree of granularity. It is both linguistically and cognitively easier to process the utterances in

Conversely, the lack of decimal places indicates (in combination with other factors) that a few minutes more or less do not matter. This allows for pragmatic vagueness. However, the use of less precise terms and loose interpretation do not imply that it is the vagueness of the less precise terms that accounts for less cognitive costs when processing them. An imprecise term such as "tall" is not only vague but also general; that is, "tall" has a larger extension than "a height of 191.02cm." A more coarse-grained degree of granularity allows thus for more generality — a property of language which clearly does make information processing easier (and also helps, as we noted, to adequately represent our inexact perceptual experiences and memories).

Whereas it might be both informationally and economically best to use a vague term, its vagueness does not become actual in most situations. Importantly, any gains in processing vague terms are lost when actually confronted with borderline cases. Then we have to think twice about what could have been meant by the vague utterance. That is why vague terms are usually not used when confronted with borderline cases; it would hinder the purposes of communication. Rather, they are used to apply to clear cases. It might thus be the case that the costs of using precise terms outweigh the expected costs of vague ones because the likelihood of actually encountering borderline cases is negligible. The risk of running into borderline cases is merely tacitly assumed.

Moreover, it is not entirely clear whether vagueness reduces cognitive costs even in clear cases. The experiments by Green and van Deemter (2011, p. 5) do, according to the authors' own conclusion, "more to cast doubt on the cost reduction hypothesis than to confirm it." They think that other linguistic properties of vague terms are actually effective in reducing the cognitive costs. Consider again replacing the term "many" with the expression "more than 1,000" when reacting to van Deemter's earthquake scenario. What is done by replacing "324,542 people" with "more than 1,000" is pruning away details, which may not be available anymore (due to a fading memory) or which may simply be irrelevant. The same effect is present when going from "324,542 people" to "many." The vague term "many" is not only more general than the precise "324,542 people," it is also shorter, grammatically less complex, and devoid of mathematical concepts. These properties alone explain why "many" is cognitively less costly than "324,542 people."

More recent and impressively careful experiments by the same authors seem to replicate these results. Although Green and van Deemter (2019, p. 83) found that instructions containing vague words tended to be processed more rapidly and more reliably by hearers than their precise equivalents, they could not rule out that "the observed benefits of vague expressions may be due to factors other than vagueness: factors like avoiding numbers, permitting comparison tasks, and range reduction" as well as granularity and the use of evaluative terms.21 Green and van Deemter (2019, p. 84) conclude that in most situations it seems to be "relatively unimportant whether a given expression is vague" or not.

Although it arguably is cost-efficient to use vague terms, it is doubtful that their vagueness is the reason for it. A reduction in cognitive costs with vague terms cannot by itself show that vagueness is valuable, that is, that borderline cases, Sorites susceptibility, or the lack of (sharp) boundaries are effective. Again, it seems that vagueness is only a side effect of other actually valuable — in this case, cognitive cost reducing — properties of vague terms. That is why premise (2) is not warranted — at least not without further evidence.

3.8 The argument from measurement

It is (surprisingly often) argued that vagueness is valuable because precision is inefficient. In particular, it is said that the use of precise terms requires unnecessary and inefficient measurement.22 Vagueness, in contrast, makes ordinary language expressions fit for everyday use. Without vagueness we would have to measure all day long the number of grains, the height of people, and the wavelength of light when all we want is to talk about heaps, tall people, and blue books. The argument can be reconstructed as follows:

It does not. It is perfectly conceivable to have a completely precise language without the need of any additional measurement. The replacement of the vague term "blue" with the precise term "blue*," the extension of which is determined by an exact range in the wavelength spectrum would not require any new measurements. Most of the time we use language such that it clearly applies. For that reason, no measurement is necessary because we do not come sufficiently close to the vicinity of the (sharp) boundary — independently of the term's vagueness or precision. Hence, we can most of time use the precise term "blue*" just as we use our ordinary language expression "blue".

On one hand, it is correct that measurement is necessary if the case at hand is close to the sharp boundary of a precise term and we want to be certain about its application to it. On the other, if the case is close to the fuzzy boundary of a vague term, we are necessarily ignorant about its application. Both precision and vagueness thus result in ignorance if we are close to the boundary of the term's extension. But precision has the additional advantage that ignorance can be resolved by measurement. Precision does not require measurement but makes it possible. Thus, premise (1) has to be rejected.

Frege's analogy — understood in this way — can be reconstructed as the following argument:

Frege was right to claim that the exactness of formal languages stems from their precision. Premise (1) is arguably correct. Also, premise (2) seems warranted. Frege's analogy suggests that formal and natural languages have complementary functions. Formal language is useful because it is precise. Natural language is useful because it is multifunctional. However, there is no explanatory link between the effects of precision in formal languages and the effects of vagueness in natural language. Lack of precision does entail much more than vagueness. It certainly does not entail that the adaptability and efficiency of natural language stems from borderline cases, Sorites susceptibility, or the lack of (sharp) boundaries.24 To draw the conclusion (3), an additional premise is needed. We would need the premise that the usefulness of imprecision entails the usefulness of vagueness — a premise that is untenable.

3.9 The argument from adaptability

A common argument for the value of vagueness is that it makes language more flexible and adaptable. In particular, it has been argued that the gradual widening of a term's extension along a Sorites series over time, and by a significant group of speakers can facilitate a change in meaning that satisfies the communicative needs of a language community. We can reformulate it in the following way:

For some reason, it seems to be particularly difficult to keep vagueness and standard relativity apart. Even van Deemter, who writes on the value of vagueness with matchless accurateness, seems to oscillate between both phenomena. He is quite explicit about his intention to talk about vague terms in the philosophical sense that they "allow borderline cases." Nevertheless, he then asks why people make "such frequent use of words whose meaning is difficult to pin down" and why it is that "their meaning varies so much from one context to the next" (van Deemter, 2010, p. 2). The first question points to polysemy (a term's property of having multiple semantically related meanings), whereas the second aims toward standard relativity or context sensitivity more generally. Van Deemter also describes vagueness and context sensitivity as two sides of the same coin, arguing that terms such as "indecent" or "vehicle" are vague "because context affects the interpretation of these words in ways that are impossible to foresee: their precisification depends on who is it that does the precisifying" (van Deemter, 2010, p. 269).

Context, of course, affects the interpretation of vague words. But what exactly is its relation to borderline cases, Sorites susceptibility, or the lack of (sharp) boundaries? Surely, vague terms can be precisified differently by different persons in different contexts. But before they can precisify them, they need to determine a context of application. This requires them to settle on a particular meaning, sense, or standard of "indecent," "tall," "blue," or "many." The impossibility to foresee in which ways context affects the interpretation of these terms stems from their property of being context sensitive — not from their vagueness.

As long as it cannot be shown how vagueness can help to achieve any of these features of language, premise (1) is unwarranted. There is no positive argument for the claim that Sorites susceptibility or the lack of (sharp) boundaries allow for gradual change in meaning. Nor is there any reason to believe that it is vagueness (and not polysemy, standard relativity, or the possibility of figurative speech) that allows the desired flexibility in the application of vague terms. Hence, neither Sorites susceptibility nor the lack of (sharp) boundaries entail that vagueness plays an interesting role in facilitating the impressive flexibility and adaptability of language that we set out to explain.

• (1) Someone desires to make other people φ.
• (2) Making a slippery slope argument by exploiting the Sorites susceptibility of vague terms is a suitable causal means to make other people φ.
• (3) If making a slippery slope argument by exploiting the Sorites susceptibility of vague terms is a suitable causal means to bring about what someone desires, then vagueness has instrumental value.
• (4) Thus: Vagueness has instrumental value.

References