verifiable (adj.)

• absolute
• actual
• apodictic
• checkable
• confirmable
• demonstrable
• factual
• historical
• incontestable
• incontrovertible
• indisputable
• indubitable
• irrefutable
• provable
• real
• self-evident
• supportable
• sustainable
• testable
• unanswerable
• undeniable
• unimpeachable
• unquestionable