Gram - SEAS

152 6 Clause-internal morphological changes
stem to which other affixes, such as inflections, can be attached. 2 Redden can, for
example, have tense attached (e.g., reddened). Even more frequently, causal relations
are expressed by lexically different forms, that is, totally fused forms, rather
than by inflectional forms, because they are at least partially idiosyncratic. 3 By
contrast, tense, aspect, and mood tend to be expressed inflectionally because they
are highly general and can apply to most event and state types. Of the languages
Bybee investigated, 72% had inflectional tense, mood, and aspect. By contrast,
only 56% had inflectional person-number-subject agreement (Bybee 1985: 33).
Although number can be expressed derivationally and even in lexically different
ways, person-number agreement tends to be less frequently bound than either
causal relations or tense-aspect-mood. This, she suggests, reflects the lesser relevance
of person-number to the verb: its prime function is not to express aspects
of the situation, but to express distinctions among arguments of the verb.
Tense, mood, and aspect themselves have ditl'erent likelihoods of ordering with
respect to each other. Aspect refers to the way in which the internal constituency
of the event is viewed, that is, according to whether it is seen as a whole from the
outside and completed (perfective), or from within and incomplete (Comrie 1976).
Tense places the situation in time with respect to an established point in time, either
the time of speech (deictic tense), or some other point in time (relational tense).
Mood refers to the way the speaker presents the truth of the proposition, whether as
probable, possible, or certain (Bybee 1985: 28). Given the hypothesis of relevance,
aspect is most relevant to the verb, tense less so, since it relates the time of the
situation to some other time, and mood least so since it expresses the speaker's
point of view on the situation. If that which is most relevant is that which is most
likely to be close to the verb, then we would expect aspect to be the most likely
of the three categories to be ordered next to the stem (or even be part of it, as a
derivational form), tense next, and mood last. The relative positions of aspect and
tense are well established for languages in which both are prefixes or both suffixes,
as illustrated by:
(15) a. Tiwi (Australia)
O:l-ru-untio-apa.
cook-PAST-DUR-eat
iT was eating it.'
b. Kewa (New Guinea)
fra-paa-ru.
cook-PERF- I SG:PAST
'I finished cooking it.' (Foley and Van Valin 1984: 210)
As Bybee notes, the claim that the natural order is mood-tense-aspect-V (or,
in OV languages, V-aspect-tense-mood), may seem counterintuitive to linguists
who speak ofT-M-A (tense-mood-aspect) in that order, and are familiar with the