The Cognitum workshop series, founded and organized by Loizos Michael and Erik T. Mueller, addresses a significant gap in automated commonsense reasoning: the acquisition of general inference rules that can be applied in novel situations. Most work is concerned with acquisition of specific facts. The first Cognitum workshop was held at IJCAI 2015 in Buenos Aires, Argentina. The second Cognitum workshop was held at IJCAI 2016 in New York. The third Cognitum workshop was held at IJCAI 2017 in Melbourne, Australia. The fourth Cognitum workshop is being held at NAACL-HLT 2018 in New Orleans, Louisiana.