It is impossible for human beings to recognize the Imam from the point of view of his being the Imam as the Imam, because no one’s senses or reason can comprehend his essence or the reality of his attributes. However, it is possible for him to be recognized from the point of view his being human, as a human creature, and it is permitted that everyone should, according to his existential rank, know and say something about their recognition of him. For the greatest expression of divine mercy to mankind is the appearance of the Imam of the Age (imam-i zaman), as a man among others, so that through him man may know God in the true sense of recognizing Him, and obey God in the true sense of obeying him.
—Nasir al-Din al-Tusi, Paradise of Submission, translation. S.J. Badakhchani, page 120
Paradise of Submission: A Medieval Treatise on Ismaili Thought