Chapter 11: Events, Qualities, Quantities, And Other Vague Words: On Lojban Abstraction
The following cmavo is discussed in this section:
du'u NU predication abstraction
There are some selbri which demand an entire predication as a sumti; they make claims about some predication considered as a whole. Logicians call these the “propositional attitudes”, and they include (in English) things like knowing, believing, learning, seeing, hearing, and the like. Consider the English sentence:
✥7.1 I know that Frank is a fool.
How's that in Lojban? Let us try:
✥7.2 mi djuno le nu la frank. cu bebna [kei] I know the event of Frank being a fool.
Not quite right. Events are actually or potentially physical, and can't be contained inside one's mind, except for events of thinking, feeling, and the like; ✥7.2 comes close to claiming that Frank's being-a-fool is purely a mental activity on the part of the speaker. (In fact, ✥7.2 is an instance of improperly marked “sumti raising”, a concept discussed further in c11-§10).
✥7.3 mi djuno le jei la frank. cu bebna [kei] I know the truth-value of Frank being a fool.
✥7.4 mi djuno le du'u la frank. cu bebna [kei] I know the predication that Frank is a fool.
Now we have it. Note that the implied assertion “Frank is a fool” is not a property of “le du'u” abstraction, but of “djuno”; we can only know what is in fact true. (As a result, “djuno” like “jei” has a place for epistemology, which specifies how we know.) ✥7.5 has no such implied assertion:
✥7.5 mi kucli le du'u la frank. cu bebna [kei] I am curious about whether Frank is a fool.
and here “du'u” could probably be replaced by “jei” without much change in meaning:
✥7.6 mi kucli le jei la frank. cu bebna [kei] I am curious about how true it is that Frank is a fool.
As a matter of convenience rather than logical necessity, “du'u” has been given an x2 place, which is a sentence (piece of language) expressing the bridi:
- x1 is the predication (the bridi), expressed in sentence x2
7.6.5) la djan. cusku le se du'u la djordj. klama le zarci [kei] John expresses the sentence-expressing-that George goes-to the store John says that George goes to the store.
✥7.6 differs from
✥7.7 la djan cusku lu la djordj. klama le zarci li'u John expresses, quote, George goes to the store, unquote. John says “George goes to the store”.
“le se du'u” is much the same as “lu'e le du'u”, a symbol for the predication, but “se du'u” can be used as a selbri, whereas “lu'e” is ungrammatical in a selbri. (See Chapter 5 for a discussion of “lu'e”.)