|Lojban For Beginners — velcli befi la lojban. bei loi co'a cilre|
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The difference between motivation and justification is not always clear, but we can say that the latter involves some rule or standard while the former does not require this. Going back to the example of Sally and the teacher, it is possible to say
la salis. te dunda lo tartcita le ctuca mu'i lenu sy. tcetoi gunka
Sally is-given a star-label [by] the teacher with-motivation she much-try work
However, this says only that Sally's hard work motivated the teacher to give her a star. It does not imply that it is the custom for teachers to give stars (or 'star-labels', as I have rather pedantically translated it) as a reward for good work. What we need here is ki'u, the sumti tcita from krinu:
We can therefore more accurately say
x1 (event/state) is a reason/justification/explanation for/causing/permitting x2 (event/state)
or, as in the earlier example,
lenu la salis. tcetoi gunka cu krinu lenu le ctuca cu dunda lo tartcita sy.
la salis. te dunda lo tartcita le ctuca ki'u lenu sy. tcetoi gunka
Note: Don't get ki'u mixed up with ku'i 'but, however'!
ki'u appeals to more general considerations than mu'i, but it still deals with human standards, not logical laws. Only a very naive student would believe that if a student is given a star, it must logically imply that that student has worked hard. In the tragic case of Fluffy, however, the fact that Fluffy is a rabbit logically implies that he will not live long, given what we know about rabbits. Here we can confidently use nibli
x1 logically necessitates/entails/implies action/event/state x2 under rules/logic system x3
actually misses out a step (the information that rabbits are short-lived) but it will do for practical purposes. If you want a textbook logic example, you can say
lenu la flufis. ractu cu nibli lenu fy. mrobi'o
the-event Fluffy is-a-rabbit implies the-event he dies
This expresses the following:
la flufis. ractu .ije ro ractu na'e ze'u jmive .i la flufis. ni'i na ze'u jmive
Fluffy is a rabbit and all rabbits are not long-lived.
Fluffy is therefore not long-lived.