# Talk:Presenting Lojban

20:08 < New> "A is everything that is not A" -- For example. Does lojban have an expression for this?

20:08 <@tsani> you can write contradictions

20:09 < New> ah.

20:09 <@tsani> since the only constraint that lojban actually places on you is a syntactic one

20:09 <@tsani> and contradictions are syntactically valid.

20:09 <@tsani> It's the semantic value of a contradiction that is debatable :)

20:09 < New> I see...

20:09 < New> Interesting.

20:10 <@tsani> for instance, we can define a predicate for which there exists nothing that can satisfy this predicate.

20:10 <@tsani> and meaningfully discuss this predicate without being confused, due to the unambiguous syntax.

20:10 < New> Nice! I'm almost convinced to learn it.

20:11 <@tsani> there is also a sort of home-grown logical system embedded in lojban predicates that allows you to use a rigidly defined system to guide you in the interpretation of these predicates.

20:12 < New> interesting.

20:12 <@tsani> lojban also has a powerful notion of scopes. For instance, the English sentence "She didn't go because her mother told her" is practically meaningless in a neutral context.

20:13 <@tsani> i.e. we can't conclude from this sentence in a neutral context whether 'she' went or not !

20:13 < ErdosNumber42> almost? I'm desperate to learn it :)

20:14 <@tsani> In Lojban, you can be precise with your negation and scopes (and other scopes, commonly called bridi operators) in order to pick out exactly which meaning you want.