Contingent Truths- Things that could be false in another state of affairs. For example, I could have not existed or I could have been born blind. Another contingent truth is that it’s possible that Obama could have not gotten re-elected or that Obama Care didn’t pass through Congress.
Necessary truths-Things that are necessarily true and can not be false. For example, 1+1=2 or 1 is not the same as 2 or there are no married bachelors. Another necessary truth is that if I am thinking, then I must exist.