The sense relating to lack of education and culture was introduced to English by Thomas Carlyle and greatly popularised by Matthew Arnold. It is derived from German student use of the term Philister to refer to the burghers of the town. This apparently derived from the use of the biblical text "the Philistines be upon you, Samson" in a memorial service for a Jena university student who died as the result of a town and gown dispute in 1693.
Sunning himself on the board steps, I saw for the first time Mr. Farquhar Fenelon Cooke. He was dressed out in broad gaiters and bright tweeds, like an English tourist, and his face might have belonged to Dagon, idol of the Philistines.
Walpole, moreover, left England not only more corrupt than he found it, but crasser and more Philistine.
1991, Nick Doll, Canoeist's Guide to the North East, page 25:
Visitors to the area are strongly recommended to have a look around the castle, for even the most Philistine of wild water canoeists cannot fail to be impressed by the enormous armoury, fine paintings and wonderful furnishings that seem to outclass all other museums and castles in the North East.
2002, Louis Auchincloss, The Heiress, in Manhattan Monologues, page 33,
Miles was taken seriously by the great dames of Manhattan society and was not scorned by even the most Philistine of their husbands.