The answer is "Ye shall know the truth and the truth shall make you free."
Wood Hall, a stone carver, carved the words "Ye shall know the truth and the truth shall make you free," on the Main Building in 1935. Born in Bloomington, Ind., Hall followed in his father's footsteps and became a stone carver as a teen. He spent nearly three weeks on scaffolding to carve the lettering on the Main Building.
Read the full history online.