Take the following as truth: The present state of the cathedral owes much to Eugane Viollet-le-Duc, who from 1845 to 1863 painstakingly restored it following the ravages of the 18th century, caused more by pre-Revolutionary meddlers than by revolutionaries who stripped it of religious symbols.
Then the following statement: "Eugane Viollet-le-Duc spent 18 years to restore the cathedral." is true, false, or inconclusive?