In early Buddhist logic, it was standard to assume that for any state of affairs there were four possibilities: that it held, that it did not, both, or neither. This is the catuskoti (or tetralemma). Classical logicians have had a hard time making sense of this, but it makes perfectly good sense in the semantics of various paraconsistent logics, such as First Degree Entailment. Matters are more complicated for later Buddhist thinkers, such as Nagarjuna, who appear to suggest that none of these options, or more than one, may hold. The point of this paper is to examine the matter, including the formal logical machinery that may be appropriate.
"THE LOGIC OF THE CATUSKOTI,"
Comparative Philosophy: Vol. 1
, Article 6.
Available at: http://scholarworks.sjsu.edu/comparativephilosophy/vol1/iss2/6