The transitive property states that if A = B and B = C, then A = C.
So, for example, if the Zika virus is not enough of a threat to cancel or postpone the Olympics in Brazil, where the virus started (A) and there have been zero reported cases of Zika from the Olympics (B) and Zika is really no big deal for the United States (C), then the Zika virus is really nothing to be concerned about. No threat in Brazil equals no Olympic cases of Zika. No Olympic cases of Zika equals no big deal to the United States. Then no threat in Brazil means no threat in the United States.
Except the Zika virus has appeared in Florida. Current efforts to contain the virus are failing. New estimates show the virus could spread throughout the American South and Southwest. And the FDA has recommended the testing of all donated blood and blood components throughout the United States to prevent the further spread of the Zika virus.
And then there’s this: