With my previous post as background and explanation of the structure of a truth table and my claim that the tetralemma has the same structure as the truth table.....with that I'll move to the tetralemma itself.
There is more than one occurance of the tetralemma in the suttas and I will use the one from DN15 (
https://www.accesstoinsight.org/tipitak ... .than.html):
"If anyone were to say with regard to a monk whose mind is thus released that 'The Tathagata exists after death,' is his view, that would be mistaken; that 'The Tathagata does not exist after death'... that 'The Tathagata both exists and does not exist after death'... that 'The Tathagata neither exists nor does not exist after death' is his view, that would be mistaken. Why? Having directly known the extent of designation and the extent of the objects of designation, the extent of expression and the extent of the objects of expression, the extent of description and the extent of the objects of description, the extent of discernment and the extent of the objects of discernment, the extent to which the cycle revolves: Having directly known that, the monk is released. [To say that,] 'The monk released, having directly known that, does not see, does not know is his opinion,' that would be mistaken.
The two statements (as required by a truth tabe) are "The Tathagata exists after death," and "The Tathagata does not exist after death".
The four possible outcomes (T/F, F/T, T/T, F/F) are "The Tathagata exists after death", "The Tathagata does not exist after death", "The Tathagata both exists and does not exist after death",and "The Tathagata neither exists nor does not exist after death".
The four possible outcomes I have shown are called "four corners" in the original post. I have not seen anything which indicates that the outcomes have any quality connected with the idea of "corners" and I consider calling them this is just a literary conventional use of analogy and not indicating that there really is some kind of corner involved. Likewise the idea that there is a "fifth corner" is in my view just a literary extention of the "four corners" analogy.
For those without formal training in math, logic, etc. I suggest that thinking of corners will not yield any truths and also looking for number five is just a distraction in that there is no fifth possible outcome to be found in the structure of the truth table (and by extention to be found in the structure of the tetralemma) and whatever this hypothetical "fifth corner" might be it must be found outside of the structure of the tetralemma.
Busy day....more later....
chownah