St. Hilary on Knowing the Trinity

Penetrate into the mystery, plunge into the darkness which shrouds that birth, where you will be alone with God the Unbegotten and God the Only-begotten. Make your start, continue, persevere. I know that you will not reach the goal, but I shall rejoice at your progress. For He who devoutly treads an endless road, though he reach no conclusion, will profit by his exertions. Reason will fail for want of words, but when it comes to a stand it will be the better for the effort made.

St. Hilary of Poitiers, On The Trinity Book II (appropriate as Trinity Sunday approaches)