Seeing is believing
Definition 1 of 1
Pro Tip 1/3Experiential Proof
Describes how personal experience or witnessing something firsthand can validate its existence or truth. 
When I saw the Northern Lights with my own eyes, I truly understood—seeing is believing.
Pro Tip 2/3Skepticism Overcome
The phrase often reflects a change from doubt to conviction after observing something directly. 
She doubted the effectiveness of the new method, but seeing is believing—the results were impressive.
Pro Tip 3/3Literal Uses
The phrase is sometimes used literally to insist on the need for visual evidence. 
After hearing the rumors of a UFO sighting, he said, 'Seeing is believing—I'll believe it when I see it.'