Final answer:
Professor Supposo likely rejected Hexagon's explanation due to lack of empirical evidence, contradicting premises, and failure to meet the burden of proof, much like G.E. Moore's rejection of skepticism based on empirical justification and the use of modus tollens.
Step-by-step explanation:
The student's question appears to concern a philosophical argument regarding justification for beliefs. This topic touches upon epistemology, which is the branch of philosophy that deals with the theory of knowledge. In the information provided, we can infer that Professor Supposo rejected Hexagon's explanation for the unusual triangle based on philosophical reasoning similar to the arguments of G.E. Moore against skepticism about the external world.
Moore argued that he had better reason to believe that he has two hands than to believe the skeptical hypothesis since he could see and feel his hands, while there was no reason to believe the skeptical hypothesis is true. The argument leads to a known form of logical reasoning in philosophy, where Moore uses modus tollens to refute the skeptic's modus ponens argument. Going by this pattern, if Supposo found shortcomings or contradictions in Hexagon's explanation akin to the lack of sensory or empirical evidence that Moore pointed out in the skeptical hypothesis, he would have a basis to reject it.
Similar to the points raised in the Outcome Assessment, Professor Supposo could have also rejected the explanation on grounds that it did not meet the burden of proof, an essential standard in establishing a logical and empirical foundation for a claim or argument.