Lord Macmillan examined previous cases and held that "the law takes no cognisance of carelessness in the abstract. It concerns itself with carelessness only where there is a duty to take care and where failure in that duty has caused damage". Whether there was a duty and breach would be examined by the standard of the reasonable person. These circumstances "must adjust and adapt itself to the changing circumstances of life. The categories of negligence are never closed". Lord Macmillan held that, according to this standard, Stevenson had demonstrated carelessness by leaving bottles where snails could access them; that he owed Donoghue a duty of care as commercial manufacturer of food and drink; and that Donoghue's injury was reasonably foreseeable. He therefore found that Donoghue had a cause of action and commented that he was "happy to think that in ... relation to the practical problem of everyday life which this appeal presents ... the principles of and Scots law are sufficiently consonant with justice and common sense to admit of the claim which the appellant seeks to establish."