Chapter 15: “No” Problems: On Lojban Negation

8. Truth questions

One application of negation is in answer to truth questions (those which expect the answers “Yes” or “No”). The truth question cmavo “xu” is in selma'o UI; placed at the beginning of a sentence, it asks whether the sentence as a whole is true or false.

✥8.1  xu la djan. pu klama la paris. .e la rom.
Is it true that:
    (John previously went-to [both] Paris and Rome.)

You can now use each of the several kinds of negation we've discussed in answer to this (presuming the same question and context for each answer).

The straightforward negative answer is grammatically equivalent to the expanded sentence with the “na” immediately after the “cu” (and before any tense/modal):

✥8.2  na go'i
[false] [repeat previous]

which means

✥8.3  la djan. [cu] na pu klama la paris. .e la rom.
John [false] previously went-to [both] Paris and Rome.
It's not true that John went to Paris and Rome.

The respondent can change the tense, putting the “na” in either before or after the new tense:

✥8.4  na ba go'i
[false] [future] [repeat previous]


✥8.5  la djan. [cu] na ba klama la paris. .e la rom.
John [false] later-will-go-to [both] Paris and Rome.
It is false that John will go to Paris and Rome.

or alternatively

✥8.6  ba na go'i
[false] [future] [repeat previous]


✥8.7  la djan. [cu] ba na klama la paris. .e la rom.
John later-will [false] go-to [both] Paris and Rome.

We stated in c15-§3 that sentences like ✥8.5 and ✥8.7 appear to be semantically identical, but that subtle semantic distinctions may eventually be found.

You can also use a scalar negation with “na'e”, in which case, it is equivalent to putting a “na'eke” immediately after any tense:

✥8.8  na'e go'i
other-than [repeat previous]

which means

✥8.9  la djan. [cu] pu na'eke klama
    [ke'e] la paris. .e la rom.
John previously other-than(went-to)
    [both] Paris and Rome.

He might have telephoned the two cities instead of going there. The unnecessary “ke” and “ke'e” would have been essential if the selbri had been a tanru.