The great Doctor of the Church St. Augustine of Hippo spent over 30 years working on his treatise De Trinitate [about the Holy Trinity], endeavoring to conceive an intelligible explanation for the mystery of the Trinity.
The Vision of St. Augustine
St. Augustine was walking by the seashore one day contemplating the mystery of the Holy Trinity when he saw a little child running back and forth from the water to a spot on the seashore. The boy was using a shell to carry water from the large ocean and pour it into a small pit that he had made in the sand.
Augustine came up to him and asked him what he was doing.
“I’m going to pour the entire ocean into this hole,” the boy replied.
“What?” said Augustine. “That is impossible, my dear child, the sea is so great and the shell and the hole are so little.”
“That is true,” the boy said. “It would be easier and quicker to draw all the water out of the sea and fit it into this hole than for you to fit the mystery of the Trinity and His Divinity into your little intellect; for the Mystery of the Trinity is greater and larger in comparison with your intelligence than is this vast ocean in comparison with this little hole.”
And then the child vanished.
What does it mean?
Some say that St. Augustine had been talking with an angel sent by God to teach him a lesson on intellectual pride. Others say it was the Christ Child Himself who came to remind Augustine of the limits of human understanding in relation to the great mysteries of our Faith.
The Sea Shell
Because of this story, the sea shell has become a symbol of St. Augustine and the study of theology.