[This post is part of a series on theories of lexical exceptionality.]

In a paper entitled simply “The treatment of exceptions”, Kisseberth (1970) proposes an interesting revision to the theory of exceptionality. Many readers may be familiar with the summary of this work given by Kenstowicz & Kisseberth 1977:§2.3 (henceforth K&K). Others may know it from the critique by Zonneveld (1978: ch. 3) or Zonneveld’s (1979) review of K&K’s book. I will discuss all of these in this post.

Kisseberth (1970)

A quick sidebar: Kisseberth’s paper is a fascinating scholarly artifact in that it probably could not be published in its current form today. (To be fair it was published in an otherwise-obscure journal, Papers in Linguistics.) For one, all the data is drawn from Matteson’s (1965) grammar of Piro;¹ the only other referenced work is SPE. Kisseberth (henceforth K) gives no page, section, or example numbers for the forms he cites. I have tried to track down some of the examples in Matteson’s book, and it is extremely difficult to find them. K gives no derivations, only a few URs, and the entire study hinges around a single rule. But it’s provocative stuff all the same.

K observes that Piro has a rule which syncopates certain stem-final vowels. He gives the following formulation:

(1) Vowel Drop:

V -> ∅ / VC __ + CV


For example, [kama] ‘to make, form’ has a nominalization [kamlu] ‘handicraft’ with nominalizing suffix /-lu/, and [xipalu] ‘sweet potato’ has a possessed form /n-xipa-lu-ne/ [nxipalne] ‘my sweet potato’.² One might think that (1) is intended to be applied simultaneously, as this is the convention for rule application in SPE, but this would predict *[nxiplne], with a medial triconsonantal cluster. Left-to-right application gives *[nxiplune]; the only way to get the observed [nxipalne] is via right-to-left (RTL) application, which I’ll assume henceforth. As far as I know, the directionality issue has not been noticed in prior work.

Of course, there are exceptions of several types. (I am drawing additional data from the unpublished paper by CUNY graduate student Héctor González, henceforth G. I will not make any attempt to make González’s transcriptions or glosses comparable to those used by K, but doing so should be straightforward.)

One type is exemplified by /nama/ ‘mouth of’, which does not undergo Vowel Drop, as in /hi-nama-ya/ [hinamaya] ‘3sgmpssr-mouth.of-Obl.’ (G 5a); under RTL application we would expect *[hinmaya]. This is handled easily in the SPE exceptionality theory I reviewed a few weeks ago by marking /nama/ as [-Vowel Drop].

However, other apparent instances of exceptionality are not so easily handled. Consider two forms involving the verb root /nika/ ‘eat’. In  /n-nika-nanɨ-m-ta/ [hnikananɨmta] ‘1sg-eat-Extns-Nondur-Vcl’ (G 5b) both vowels of the root satisfy (1) but do not undergo syncope. One might be tempted to mark this root as [-Vowel Drop], but it does undergo deletion in other derivations, such as in /nika-ya-pi/ [nikyapi] ‘eat-Appl-Instr.Nom’ (G 4d). Rather, it seems to be that the following /-nanɨ/ fails to trigger deletion. This is not easily handled in the SPE approach. K gives a number of similar examples involving the verbal theme suffixes /-ta/ and /-wa/, which also do not trigger syncope. If a morphemes vary in whether or not they undergo and whether or not they trigger Vowel Drop, one can imagine that these properties might cross-classify:

• Mutable, catalytic The nominalizing suffix /-lu/, discussed above, is both  mutable (i.e., undergoes syncope), and catalytic (triggers syncope) in /n-xipa-lu-ne/ [nxipalne].
• Inalterable, catalytic I have not found any relevant examples in Piro; Kenstowicz & Kisseberth 1977 (118f.) present a hastily-described example from Slovak.
• Mutable, quiescent /meyi-wa-lu/ [meyiwlu] ‘celebration’ shows that intranstive verb theme suffix /-wa/ is mutable but quiescent (does not trigger syncope; *[meywalu]).
• Inalternable, quiescent /yimaka-le-ta-ni-wa-yi/ shows that the imperfective suffix /-wa/ (not to be confused with the homophonous intransitive /-wa/) is inalterable; /r-hina-wa/ [rɨnawa] ‘3-come-Impfv’ (G 6c) shows that it is quiescent (*[rɨnwa]).

According to G, there is also one additional category that does not fit into the above taxonomy: the elative suffix /-pa/ triggers deletion of the penultimate (rather than preceding) vowel, as in /r-hitaka-pa-nɨ-lo/ [rɨtkapanro] ‘3-put-Evl-Antic-3sgf’ (G 7a). Furthermore, /-pa/ appears to lose its catalytic property when it undergoes syncope, as in /cinanɨ-pa-yi/ [cinanɨpyi] ‘full-Elv-2sg’ (G 7c). Given the rather unexpected set of behaviors here, apparently confined to a single suffix, I wonder if this is the full story.

Having reviewed this  data, I don’t have an abundance of confidence in it, particularly given K’s hasty presentation. However, K has identified something not obviously anticipated by the SPE theory. K’s proposal is a simple extension of the SPE theory; in addition to rule features for the target, we also need rule features for the context. For instance, inalterable, quiescent imperfective marker /-wa/,⁴ which neither undergoes nor triggers Vowel Drop, would be underlyingly [-rule Vowel Drop, –env. Vowel Drop]. Then, the rule interpretative procedure applies a rule R when its structural description is met, when the target is [+rule R], and when the all morphemes in the context are [+env. R].

Zonneveld (1978, 1979)

I have already gone on pretty long, but I should briefly discuss what subsequent writers have had to say about this proposal. Kenstowicz & Kisseberth (1977, henceforth K&K), perhaps unsurprisingly endorse the proposal, and provide some very hasty examples of how one might use this new mechanism. Zonneveld (henceforth Z), in turn, is quite critical of K’s theory. These criticisms are laid out in chapter 3 of Zonneveld 1978 (a published version of his doctoral dissertation), which reviews quite a bit of contemporary work dealing with this issue. The 1978 book chapter (about 120 typewritten pages in all) is a really good review; it is well organized and written, and full of useful quotations from the sources it reviews, and while it is somewhat dense it is hard to imagine how it could be made less so. Z reprises the criticisms of K’s theory briefly, and near verbatim, in his uncommonly-detailed review of K&K’s book (Zonneveld 1979). Z has several major criticisms of rule environment theory.

First, he draws attention to an example on where the conventions proposed by K will fail; I will spell this out in a bit more detail than Z does. The key example is /w-čokoruha-ha-nu-lu/ [wčokoruhahanru] ‘let’s harpoon it’. The anticipatory /-nu/ is mutable (but quiescent) and it is in the phonological context for syncope. To its left is the ‘sinister hortatory’ /-ha/, and this is known to be quiescent because it does not trigger deletion of the final vowel in /čokoruha/; cf. /čokoruha-kaka/ [čokoruhkaka] ‘to cause to harpoon’, which shows that the substring /…čokoruha-ha…/ does not undergo deletion because /-ha/ is quiescent rather than because /čokoruha/ is inalterable. To its right is the catalytic /-lu/. By K’s conventions, syncope should not apply to the /u/ in the anticipatory morpheme because /-ha/, in the left context, is [-env. Vowel Drop], but in fact it does. Z anticipates that one might want to introduce separate left and right context environment features: maybe /-ha/ is [+left env. Vowel Drop, -right env. Vowel Drop]. The following additional issues suggest the very idea is on the wrong track, though.

Seccondly, Z shows that rule environment features cause additional issues if one adopts the SPE conventions. The /-ta/ in /yona-ta-nawa/ [yonatnawa] ‘to paint oneself’ is presumably quiescent because it fails to trigger syncope in /yona/.⁵  Thus we would expect it to be lexically [-env. Vowel Drop], and for this specification to percolate to the segments /t/ and /a/. (I referred to this as Convention 2 in my previous post, and K adopts this convention.) However, it is a problem for this specification to be present on /t/, since that /t/ is itself in the left context for Vowel Drop, and this would counterfactually block its application to the second /a/! This is schematized below.

(2) Structural description matching for /yona-ta-nawa/

   VCVCV
yonatanawa

As a related point, Z points out that there many cases where under K’s proposal it is arbitrary whether one uses rule or environmental exception features. For instance, in the famous example obesity, the root-final s is part of the structural context so the root could be marked [-rule Trisyllabic Shortening], which would percolate to the focus e, or it could be marked [-env. Trisyllabic Shortening], which would percolate to the right-context s, or both; all three options would derive non-application. This is also schematized below.

(3) Structural description matching for obesity:

  VC-VCV
obes-ity

Z continues to argue that a theory that distinguishes between leftward and rightward contextual exceptionality also will not go through. Sadly, he does not provide a full analysis of the Piro facts in his preferred theory.

Z has a much more to say about the (then-)contemporary literature on rule exceptionality. For example, he discusses an idea, originally proposed by Harms (1968:119f.) and also exemplified by Kenstowicz (1970), that there are exceptions such that a rule applies to morphemes that do not meet its (phonologically defined) structural description. While he does seem to accept this, possible examples for such rules is quite thin on the ground,  and the very idea seems to reflect the mania for minimizing rule descriptions and counting features that—and this is not just my opinion—polluted early generative phonology. If one rejects this frame, it is obvious that the effect desired can be simulated with two rules, applied in any order. The first will be a phonologically general one (with or without negative exceptions); the second will be the same change but targeting certain morphemes using whatever theory of exceptionality one prefers. Indeed, most examples of rules applying where their structural description is not met are already disjunctive, and I doubt whether such rules are really a single rule in the first place.

The ultimate theory Z settles on is one quite similar to that proposed by SPE. First, readjustment rules introduce rule features like [+R] and these handle simple exceptions of the obesity type. Z proposes further that such readjustment rules must be context-free, which clearly rules out using this mechanism for phonologically defined classes of negative exceptions; cf. (4-5) in my previous post.  Secondly, Z proposes that so-called morphological features like Lightner’s [±Russian] will be used for deriving what we might now call “stratal” effects: morphemes that are exceptions to multiple rules. For instance, if we have three rules A, B, C that all [-Russian] morphemes are exceptions to, then context-free redundancy rules will introduce the following rule features.

(4)
[-Russian] -> {-A}
[-Russian] -> {-B}
[-Russian] -> {-C}

Z replays several arguments from Lightner about why morphological of this sort should be distinguished from rule features; I won’t repeat again them here. Finally, Z derives minor rules via readjustment rules triggered by so-called “alphabet” features. For instance, let us again consider umlauting English plurals like goose–geese. Z supposes, adding some detail to a sketchier portion of the SPE proposal, that morphemes targeted by umlaut are marked [+G] (where G is some arbitrary feature). There are two ways one could imagine doing this.

First, either the underlying form, /guːs/ perhaps, could be underlyingly [+G]. Then, let us assume that umlauting is simply fronting in the context of a Plural morphosyntactic feature, and that subsequent phonological adjustments (like the diphthongization in mouse–mice) are handled by later rules. Then it is possible to write this as follows:

(5) Umlaut (variant 1): [+Back, +G] -> {-Back} / __ [+Plural]

This rule is phonologically “context-free”, but its application is conditioned by the presence of the alphabet feature specification in the focus and the morphosyntactic feature in the context. I will take up the question of whether such rules are always phonologically context-free in a (much) later post.

I suspect that the analysis in (5) is the one Z has in mind, and it is also seems to be the orthodoxy in Distributed Morphology (henceforth DM); see, e.g., Embick & Marantz 2008 and particularly their (4) for a conceptually similar analysis of the English past tense. Applying their approach strictly would lead us to miss the generalization (if it is in fact a linguistically meaningful generalization) that umlauting plurals all have a null plural suffix. Umlauting plurals have an underlying feature [+G] (there is no “list” per se; it is just), but their rules of exponence also need to “list” these umlauting morphemes as exceptionally selecting the null plural rather than the regular /-z/. It seems to me this is not necessary because the rules of exponence for the plural maybe could be sensitive to the presence or absence of [+G]. This would greatly reduce the amount of “listing” necesssary. (I do not have an analysis of—and thus put aside—the other class of zero plurals in English, mass nouns like corn.)

(6) Rules of exponence for English noun plural (variant 1):

a. [+Plural] <=>  ∅       / __ [+G]
b.                     <=> -ɹɘn / __ {√CHILD, …}
c.                      <=> -ɘn / __ {√OX, …}
d.                      <=> -z   / __

Secondly and more elaborately, one could imagine that [+G] is inserted by—i.e., and perhaps, is the expression of—plurality for umlauting morphemes. In piece-based realizational theories like DM, affixes are said to expone (and thus delete) syntactic uninterpretable features. One possibility (which brings this closer to amorphous theories without completely discarding the idea of morphs) is to treat insertion of [+G] as an exponent of plurality.

(7) Rules of exponence for English noun plural (variant 2):

a. [+Plural] <=> {+G} / __ {√GOOSE, √FOOT, √MOUSE, …}
b.                     <=> -ɹɘn  / __ {√CHILD}
c.                     <=> -ɘn    / __ {√OX}
d.                     <=> -z      / __

(7a) and (7b-d) implicate different types of computations—the former inserts an alphabet feature, the latter inserts vocabulary items—but I am supposing here that they can be put into competition. Under this alternative analysis, umlaut no longer requires a morphosyntactic context:

(8) Umlaut (variant 2): [+Back, +G] -> {-Back}

Beyond precedent, I do not see any reason to prefer analysis (5-6) over (7-8). Either can clearly derive what Lakoff called minor rules, though they differ in how exceptionality information is stored/propagated, and thus may have interesting consequences for how we relate the major/minor class distinction to theories of productivity. I have written enough for now, however, and I’ll have to return to that question and others another day.

Endnotes

1. I too will refer to this language as Piro, as do Matteson and Kisseberth. It should not be confused with unrelated language known as Piro Pueblo. Some subsequent work on this phenomenon refer to the language as Yine (and say it “was previously known as Piro”), though I also found another source that says that Yine is simply a major variety of Piro. I have been unable to figure out whether there’s a preferred endonyms.
2. I am not prepared to rule out the possibility that /xipa/ is itself an exception (“inalterable”), but all evidence is consistent with RTL application.
3. In his endnote 2, K says the rule is even narrower than stated above, since it does not apply to monosyllabic roots. However, he might have failed to note that this condition is implicit in his rule, if we interpret (11) strictly as holding that the left context should be tautomorphemic. Piro requires syllables to be consonant-initial, so the minimal bisyllabic roots is CV.CV. Combining this observation with (1), we see that the shortest root which can undergo vowel deletion is also bisyllabic, since concatenating the left context and target gives us a bisyllabic VCV substring. In fact, things are more complicated because monosyllabic suffixes do undergo syncope; many examples are provided above. Clearly, the deleting vowel need not be tautomorphemic with the preceding vowel, contrary to what a strict reading of the “+” in (1) would seem to imply. According to González, syncope imposes no constraints on the morphological structure of its context except that it only applies in derived environments—CVCVCV trisyllables like /kanawa/ ‘canoe’ surfaces faithfully as [kanawa], not *[kanwa]—and is subject to lexical exceptionality discussed here. 
4. K glosses this as ‘still, yet’.
5. As was the case with /xipa/ in endnote 2, we’d like to confirm that /yona/ is mutable rather than inalterable, but one does not simply walk into Matteson 1965.

References

Embick, D. and Marantz, A. 2008. Architecture and blocking. Linguistic Inquiry 39(1): 1-53.
González, H. 2023. An evolutionary account of vowel syncope in Yine. Ms., CUNY Graduate Center.
Harms, R. T. 1968. Introduction to Phonological Theory. Prentice-Hall.
Kenstowicz, M. 1970. Lithuanian third person future. In J. R. Sadock and A. L. Vanek (ed.), Studies Presented to Robert B. Lees by His Students, pages 95-108. Linguistic Research.
Kenstowicz, M. and Kisseberth, C. W. 1977. Topics in Phonological Theory. Academic Press.
Kisseberth, C. W. 1970. The treatment of exceptions. Papers in Linguistics 2: 44-58.
Matteson, E. 1965. The Piro (Arawakan) Language. University of California Press.
Zonneveld, W. 1978. A Formal Theory of Exceptions in Generative Phonology. Peter de Ridder.
Zonneveld, W. 1979. On the failure of hasty phonology: A review of Michael Kenstowicz and Charles Kisseberth, Topics in Phonological Theory. Lingua 47: 209-255.

[Minor correction: after rereading Zonneveld 1978, I think Lakoff misrepresents the SPE theory slightly, and I repeated his mispresentation in what I wrote. Lakoff writes that the SPE theory could have phonological rules that introduce minus-rule features. In fact C&H say (374-5) that they have found no compelling examples of such rules and that they “propose, tentatively” that such rules “not be permitted in the phonology”; any such rules must be readjustment rules, which are assumed to precede all phonological rules. This means that (4-5) are probably ruled out. Lakoff’s mistake may reflect the fact that the 1970 book is a lightly-adapted version of his 1965 dissertation, for which he drew on a pre-publication version of SPE.]

Recently I have attempted to review and synthesize different theories of what we might call lexical (or morpholexical or morpheme-specific) exceptionality. I am deliberately ignoring accounts that take this to be a property of segments via underspecification (or in a few cases, pre-specification, usually of prosodic-metrical elements like timing slots or moras), since I have my own take on that sort of thing under review now. Some takeaways from my reading thus far:

• This is an understudied and undertheorized topic.
• At the same time, it seems at least possible that some of these theories are basically equivalent.
• Exceptionality and its theories play only a minor role in adjudicating between competing theories of phonological or morphological representation, despite their obvious relevance.
• Also despite their obvious relevance, theories of exceptionality make little contact with theories of productivity and defectivity.

Since most of the readings are quite old, I will include PDF links when I have a digital copy available.

Today, I’m going to start off with Chomsky & Halle’s (1968) Sound Pattern of English (SPE), which has two passages dealing with exceptionality: §4.2.2 and §8.7. While I attempt to summarize these two passages as if they are one, they are not fully consistent with one another and I suspect they may have been written at different times or by different authors. Furthermore, it seemed natural for me to address, in this same post, some minor revisions proposed by Lakoff (1970: ch. 2). Lakoff’s book is largely about syntactic exceptionality, but the second chapter, in just six pages, provides important revisions to the SPE system. I myself have also taken some liberties filling in missing details.

Chomsky & Halle give a few examples of what they have in mind when they mention exceptionality. There is in English a rule which laxes vowels before consonant clusters, as in convene/conven+tion or (more fancifully) wide/wid+th. However, this generally does not occur when the consonant cluster is split by a “#” boundary, as in restrain#t.¹ The second, and more famous, example involves the trisyllabic shortening of the sort triggered by the -ity suffix. Here laxing also occurs (e.g., serene–seren+ity, obscene–obscen+ity) though not in the backformation obese-obesity.² As Lakoff (loc. cit.:13) writes of this example, “[n]o other fact about obese is correlated to the fact that it does not undergo this rule. It is simply an isolated fact.” Note that both of these examples involve underapplication, and the latter passage gives more obesity-like examples from Lightner’s phonology of Russian, where one rule applies only to “Russian” roots and another only to “Church Slavonic” roots.

SPE supposes that by default, that there is a feature associated with each rule. So, for instance, if there is a rule R there exists a feature [±R] as well. A later passage likens these to features for syntactic category (e.g., [+Noun]), intrinsic morpho-semantic properties like animacy, declension or conjugation class features, and the lexical strata features introduced by Lees or Lightner in their grammars of Turkish and Russian. SPE imagine that URs may bear values for [R]. The conventions are then:

(1) Convention 1: If a UR is not specified [-R], introduce [+R] via redundancy rule.
(2) Convention 2: If a UR is [αR], propagate feature specification [αR] to each of its segments via redundancy rule.
(3) Convention 3: A rule R does not apply to segments which are [-R].

Returning to our two examples above, SPE proposes that obese is underlylingly [−Trisyllabic Shortening], which accounts for the lack of shortening in obesity. They also propose rules which insert these minus-rule features in the course of the derivation; for instance, it seems they imagine that the absence of laxing in restraint is the result of a rule like V → {−Laxing} / _ C#C, with a phonetic-morphological context.

Subsequent work in the theory of exceptionality has mostly considered cases like obesity, the rule features are present underlyingly but with one exception, discussed below, the restraint-type analysis, in which rule features are introduced during the derivation, do not seem to have been further studied. It seems to me that the possibility of introducing minus-rule features to a certain phonetic context could be used to derive a rule that applies to unnatural classes. For example, imagine an English rule (call it Tensing) which tenses a vowel in the context of anterior nasals {m, n} and the voiceless fricatives {f, θ, s, ʃ} but not voiced fricatives like {v, ð}.³ Under any conventional feature system, there is no natural class which includes {m, n, f, θ, s, ʃ} but not also {ŋ, v}, etc. However, one could derive the desired disjunctive effect by introducing a -Tensing specification when the vowel is followed by a dorsal, or by a voiced fricative. This might look something like this:

(4) No Tensing 1: [+Vocalic] → {−Tensing} / _ [+Dorsal]
(5) No Tensing 2: [+Vocalic] → {−Tensing} / _ [-Voice, +Obstruent, +Continuant]

This could continue for a while. For instance, I implied that Tensing does not apply before a stop so we could insert a -Tensing  specification when the following segment is [+Obstruent, -Continuant], or we could do something similar with a following oral sonorant, and so on. Then, the actual Tensing rule would need little (or even no) phonetic conditioning.

To put it in other words, these rules allow the rule to apply to a set of segments which cannot be formed conjunctively from features, but can be formed via set difference.⁴ Is this undesirable? Is it logically distinct from the desirable “occluding” effect of bleeding in regular plural and past tense allomorphy in English (see Volonec & Reiss 2020:28f.)? I don’t know. The latter SPE passage seems to suggest this is undesirable: “…we have not found any convincing example to demonstrate the need for such rules [like my (4-5)–KBG]. Therefore we propose, tentatively, that rules such as [(4-5)], with the great increase in descriptive power that they provide, not be permitted in the phonology.” (loc cit.:375). They propose instead that only readjustment rules should be permitted to introduce rule features; otherwise rule feature specifications must be underlyingly present or introduced via redundancy rule.

As far as I can see, SPE does not give any detailed examples in which rule feature specifications are introduced via rule. Lakoff however does argue for this device. There are rules which seem to apply to only a subset of possible contexts; one example given are the umlaut-type plurals in English like foot–feet or goose–geese. Later in the book (loc. cit./, 126, fn. 59) the rules which generate such pairs are referred to these as minor rules. Let us call the English umlauting rule simply Umlaut. Lakoff notes that if one simply applies the above conventions naïvely, it will be necessary to mark a huge number of nouns—at the very least, all nouns which have a [+Back] monophthong in the final syllable and which form a non-umlauting plural—as [-Umlaut]. This, as Lakoff notes, would wreck havoc on the feature counting evaluation metric (see §8.1), and would treat what we intuitively recognize as exceptionality (forming an umlauting plural in English) as “more valued” than non-exceptionality. Even if one does not necessarily subscribe to the SPE evaluation metric, one may still feel that this has failed to truly encode the productivity distinction between minor rules and major rules that have exceptions. To address this, Lakoff proposes there is another rule which introduces [–Umlaut], and that this rule (call it No Umlaut) applies immediately before Umlaut. Morphemes which actually undergo Umlaut are underlying -No Umlaut. Thus the UR of an noun with an umlauting plural, like foot, will be specified [–No Umlaut], and this will not undergo a rule like the following:

(6) No Umlaut: [ ]  → {–Umlaut}

However, a noun with a regular plural, like juice, will undergo this rule and thus the umlauting rule U will not apply to it because it was marked [-U] by (6).

One critique is in order here. It is not clear to me why SPE introduces (what I have called) Convention 2; Lakoff simply ignores it and proposes an alternative version of Convention 3 where target morphemes, rather than segments, must be [+R] to undergo rule R. Of his proposal, he writes: “This system makes the claim that exceptions to phonological rules are morphemic in nature, rather than segmental.” (loc. cit., 18) This claim, while not necessarily its 1970-era implementation, is very much in vogue today. There are some reasons to think that Convention 2 introduces unnecessary complexities, which I’ll discuss in a subsequent post. One example (SPE:374) makes it clear that for Chomsky & Halle, Convention 3 requires that that for rule R the target be [+R], but later on, they briefly consider what if anything happens if any segments in the environment (i.e., structural change) are [-R].⁵ They claim (loc. cit., 375) there are problems with allowing [-R] specifications in the environment to block application of R, but give no examples. To me, this seems like an issue created by Convention 2, when one could simply reject it and keep the rule features at the morpheme level.

[This post, then, is the first in a series on theories of lexical exceptionality.]

Endnotes

1. The modern linguist would probably not regard words like restraint as  subject to this rule at all. Rather, they would probably assign #t to the “word” stratum (equivalent to the earlier “Level 2”) and place the shortening rule in the “stem” stratum (roughly equivalent to “Level 1”). Arguably, C&H have stated this rule more broadly than strictly necessary to make the point.
2. It is said that the exceptionality of this pair reflects its etymology: obese was backformed from the earlier obesity. I don’t really see how this explains anything synchronically, though.
3. This is roughly the context in which Philadelphia short-a is tense, though the following consonant must be tautosyllabic and tautomorphemic with the vowel. Philadelphia short-a is, however, not a great example since it’s not at all clear to me that short-a tensing is a synchronic process.
4. Formally, the set in question is something like [−Dorsal] ∖ [+Voice, +Consonantal, +Continuant, −Nasal].
5. This issue is taken up in more detail by Kisseberth (1970); I’ll review his proposal in a subsequent post.

References

Chomsky, N. and Halle, M. 1968. Sound Pattern of English. Harper & Row.
Kisseberth, C. W. 1970. The treatment of exceptions. Papers in Linguistics 2: 44-58.
Lakoff, G. 1970. Irregularity in Syntax. Holt, Rinehart and Winston.