The Guardians are the evidence of the maturity of mankind

STATEMENTS MADE BY SHOGHI EFFENDI ON THE COVENANT AND 'ABDU'L-BAHÁ'S WILL AND THE RELATION OF THAT WILL TO THE FIRST GUARDIAN'S ACTIONS
"The Guardians are the evidence of the maturity of mankind in the sense that at long last men have progressed to the point of having one world, and of needing one world management for human affairs. In the spiritual realm they have also reached the point where God could leave, in human hands (i.e. the Guardians'), guided directly by the Báb and Bahá’u’lláh, as the Master states in His Will, the affairs of His Faith for this Dispensation. This is what is meant by 'this is the day which will not be followed by the night'. In this Dispensation, divine guidance flows on to us in this world after the Prophet's ascension, through, first the Master, and then the Guardians." (The Bahá'í News, June, 1950, p. 8; #1047 of Lights of Guidance, p. 311)