Sentence:  A contrast of the scripture reading of , let us say , St. Augustine , John Bunyan , and Thomas Jefferson , all <WSD>three</WSD> of whom found in such study a real source of enlightenment , can tell us a great deal about these three men and the age that each represented and helped bring to conscious expression . 
Meaning of the word marked with <WSD> tags:  the cardinal number that is the sum of one and one and one