Analogical reasoning in the law

In the last video, we saw how we reason analogically. We proceed from the observation that two or more things are similar in some respects, to the conclusion that they are probably similar in some other respect, as well. Here’s how this applies in law. In August, 1928, Mrs. May Donaghue and a friend went into the Wellmeadow Cafe in Paisley, Scotland. The friend bought her ice cream and ginger beer to make a soda. The ginger beer came in an opaque glass bottle. The shopkeeper poured some of the ginger beer into a glass over the ice cream. Mrs. Donahue drank some, and her friend poured the rest of the ginger beer in the glass for her.

But, as she did so, a partially decomposed snail floated out of the bottle. “In sequence of the nauseating sight of the snail in such circumstances, and of the noxious condition of the said snail-tainted ginger beer consumed by her, Mrs. Donaghue sustained shock, and indeed, illness.” Mrs. Donaghue sued the ginger beer manufacturer, Stevenson, climbing 500 pound. Now most lawyers would probably have told her that she was wasting her time and money. You could then sue in negligence only if you had a contract under which someone owed you a duty of care. And Mrs. Donaghue had no contract– not with the shopkeeper– her friend had bought the ginger beer– or with the manufacturer, whose contract was with the shopkeeper. But remarkably, Mrs.

Donaghue won. And in one of the most important cases in western legal history, the tort of negligence was born. Now the judgement in Donaghue and Stevenson, itself involves complex analogical reasoning, as the judge, Lord Atkin, finds authority for his decision in various proceeding cases and extra legal material, including the Bible. But we see the mode of reasoning more clearly in decisions that follow the snail in the ginger beer case. Donaghue itself might have been read as establishing a fairly narrow principle.

On one reading, just this– “A manufacturer of products, which he sells in such a form as to show that he intends them to reach the ultimate consumer in the form in which they left him with no reasonable possibility of intermediate examination, and with the knowledge that the absence of reasonable care in the preparation or putting up of the products will result in an injury to the consumer’s life or property, owes a duty to the consumer to take that reasonable care.” Analogical reasoning, however, allowed the courts to quickly move beyond that narrow principle. In the early 1930s, around the same time that Mrs. Donahue was enjoying– or not enjoying– her soda in Paisley, a Dr.

Grant was buying a pair of woollen underpants in Adelaide, Australia. The underpants came wrapped in paper. Unfortunately, for Doctor Grant, the manufacturer hadn’t washed a caustic solution out of the underpants. And he, having apparently worn them for an entire week without washing them, developed a very serious, almost fatal, dermatitis. The Court in Grant and the Australian Knitting Mills, lists the features they take to be central in the then recent and revolutionary Donaghue’s case. A manufacturer had to sell products in a form in which he intended them to reach the ultimate consumer. There had to be no reasonable opportunity for the consumer to examine the product before consumption.

The manufacturer had to know that if he didn’t take reasonable care, his product posed a risk to the consumer. And if features one, two, and three were present, so was a new feature– a legal duty of care to the consumer. And, say the Australian Court, Grant’s case resembles Donaghue’s. One, Australian Knitting Mills sold the underpants in the form they intended them to be worn. Two, though they were wrapped in paper, and not sealed in a bottle, the consumer couldn’t have seen the caustic solution by looking at the underpants. Three, the manufacturer knew, or ought to have known that wearing caustic underpants might be very, very bad for you.

And so since Grant resembled Donahue in those respects, it also had the further feature– a duty of care and so liability. Putting it in our schema– one, Grant’s case is similar to Donaghue’s case– it shares features one to three. Two, Donaghue’s case has the further feature– a duty of care and liability. Three, therefore, Grant’s case also has that further feature. The judges in the caustic underpants case, in other words, reasoned by analogy. Looking for similarities, interpreting or setting aside some– the fact the underpants weren’t in a sealed container and weren’t food didn’t matter. They were like the colour of the car.

Before saying, this case is similar to that one, and therefore the extra property– a duty of care– applies in Grant because it applied in the ginger beer case. Reasoning by analogy is central to legal reasoning. It allows lawyers and judges to pay proper regard to previous decisions, while also allowing them to extend those decisions, to work out which similarities really matter. And it can do that in a logical and critical thinking outside the law as well.