This research essay illustrates how the IS discipline might pursue systems theories with the goal of understanding IS in new ways, generating innovative and useful systems theories, and achieving more impact in the world. It discusses recent articles that compare different perspectives and expectations related to theories and theorizing in the IS discipline. It uses the term domain-specific systems theory (DSST) to accentuate the difference between general systems theory (GST) and specific systems theories. It provides examples illustrating how DSSTs can illuminate important concerns that variance and process perspectives do not address directly. It shows how work system theory (WST) and several of its extensions are DSSTs that provide useful lenses for understanding, analyzing, and theorizing about systems in organizations. It concludes by summarizing ways in which the IS discipline might welcome systems theories more wholeheartedly.