This is not needed, as tautologies can already be obtained with kau,
the indirect question marker.
da'au is equivalent to xukau, which stands for the answer
to xu, which answer must by definition be whatever makes the
sentence true.
That might work, but then how do you get the paradox operator (though admittedly it's much less useful.)
This can be useful in some "maybe, maybe not" contexts. For example:
- John may or may not love Betty.
- la djan. da'au prami la betis.
It also might be useful to add an experimental cmavo with the same meaning to NAI, so that this can be used in logical constructions.
If anyone is interested in a unary operator which always returns false, one can use "na da'au".
We would need further justification for {da'au}, because that one
example could be said as:
- da jei la djan prami la betis
- = Something is the truth value of that J loves B
--And.
That changes the structure of the sentence. We can also get a tautology with ganai la djan prami la betis gi la djan prami la betis, but it changes the structure and so is not acceptable. xukau might be good though.
Also, we can borrow from three-value logic and use sairu'e. Thus:
- .i la djan cu sairu'e prami la betis
- It is possible that it is likely that John loves Betty.