In the hair-pulling case, what we have is not two events which are physically connected, like clouds and rain, but three events:

  1. Joey pulls Sally's hair.

  2. Sally decides, as a result of this, to hit Joey.

  3. Sally hits Joey.

For the sake of convenience, English misses out the second event and says "Sally hit Joey because he pulled her hair." However, this is not only vague but, some would say, psychologically dangerous. People do not generally react to stimuli automatically, but as a result of motivation, and confusing complex responses with simple physical causation may lead us to believe that we have no control over our emotions or even our actions. Whether or not we believe in free will at a metaphysical level, it is useful to distinguish between physical reactions and responses which have a cognitive/emotional element. Not surprisingly, then, Lojban has a separate gismu for motivation: mukti. The full definition of mukti is

x1 (action/event/state) motivates/is a motive/incentive for action/event x2, per volition of x3

We can therefore say

lenu do lacpu lei kerfa [pe la salis.] cu mukti lenu la salis. darxi do [kei la salis]
the-event you pull the-mass hair [related-to Sally] motivates the-event Sally hit you [through the volition of Sally]
Your pulling Sally's hair motivated her to hit you.

As we can see, the third place is nearly always unnecessary, since we can assume that the agent of the second event is also the person who decides to do it. Even so, this structure is a bit clumsy, so again we would normally use a sumti tcita — in this case, mu'i. This gives us

la salis. darxi do mu'i lenu do lacpu lei kerfa
Sally hits you with-motive you pull the-mass hair

Exercise 1

Don't bother to translate these sentences, just decide whether they should use ri'a or mu'i.

  1. The can exploded because it was hot.

  2. I felt afraid because I heard a noise.

  3. The people revolted because of the high taxes.

  4. The bread is moldy because you left it in the plastic wrapper.

  5. Prices have risen because of excessive wage claims.