WordNet sense 1 (based on known statements or events or conditions):

legitimate, legitimate

WordNet sense 2 (well grounded in logic or truth or having legal force):

valid

WordNet sense 3 (capable of thinking and expressing yourself in a clear and consistent manner):

coherent, lucid

WordNet sense 4 (consistent with or based on or using reason):

rational

WordNet sense 5 (marked by an orderly, logical, and aesthetically consistent relation of parts):

consistent, ordered, orderly