Question: Which were the philosophers whose primary interest was Natural philosophy?
SPARQL:
SELECT DISTINCT ?uri WHERE {?uri <http://dbpedia.org/property/mainInterests> <http://dbpedia.org/resource/Natural_philosophy>  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Philosopher>}