Match the famous men with their occupations samuel johnson, samuel pepys, adam smith, and oliver cromwell political leader philosopher lexicographer diarist

The political leader is Oliver Cromwell. He was in the military and he was a statesman in England, Scotland and in Ireland. 

Adam Smith was a philosopher. He was a Scottish political economist as well. 

Samuel Johnson was a writer of dictionaries, also known as a lexicographer.

Lastly, Samuel Pepys was famous for keeping a diary for about a decade. So he is the diarist.