Sine Qua Non Definition: Latin: without which, not. Related Terms: But For, Causa Sine Qua Non Ballentine's defines sine qua non as: "Without which it is not. An indispensable prerequisite." Sine qua non is an essential concept in the law of negligence. As Justice Cady of the Court of Appeals of Iowa wrote in Sumpter v. City of Moulton: "The test to determine the actual cause prong of causation is known as sine qua non; but for the defendant's conduct, the harm would not have occurred." Or these words of Justice Murray Schwartz of the United States District Court (Delaware) in Clime v Dewey Beach: "Delaware follows a but for or sine qua non rule of causation. Under this rule, the defendant's conduct is a cause of the event if the event would not have occurred but for that conduct; conversely, the defendant's conduct is not a cause of the event, if the event would have occurred without it." REFERENCES: Ballentine, James, Ballentine's Law Dictionary (Rochester, New York: Lawyers Co-operative Publishing Company, 1969), page 1182 Clime v. Dewey Beach Enterprises, 831 F. Supp. 341 (1993) Duhaime, Lloyd, Legal Definition of Causa Sine Qua Non Duhaime, Lloyd, Tort & Personal Injury Law Sumpter v. City of Moulton, 519 NW 2d 427 (1994) Categories & Topics: Dictionary of Latin Law Terms Tort and Personal Injury Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!