God has “endowed every soul with the capacity to recognize the signs of God”

He[God] hath endowed every soul with the capacity to recognize the signs of God. How could He, otherwise, have fulfilled His testimony unto men, if ye be of them that ponder His Cause in their hearts. He will never deal unjustly with any one, neither will He task a soul beyond its power. He, verily, is the Compassionate, the All-Merciful. 
(Baha'u'llah, Gleanings from the Writings of Baha'u'llah)