"A picture frequently seen and known as the Vision of Saint Augustine illustrates the legend that, as the saint walked on the seashore, he saw a child who, having dug a hole in the sand, was filling it with water. When the saint asked the child what he did, the child replied that he intended to pour all the water of the sea into this hole."When the saint assured him that such a task could never be finished, the child replied, "It is no more impossible to do this than for thee to comprehend and explain the mystery on which thou art meditating!""
Augustine had a Christian mother and a pagan father. I don't think he saw Mani as non-Christian. The Manicheans were very helpful to him in the nine years he followed their system. He certainly appreciated their philosophy of freedom!