Unfortunately, it is often very difficult to understand why the law adopts one course rather than another. This is largely because the courts have rarely articulated clearly the reasons which motivate them in making decisions of this nature. Instead, they explain their decisions in ‘conceptual’ language, that is, they place the case in a certain legal category and they then apply the rules appropriate to that category. The decision then appears to be dictated by pure logic, but in fact the crucial part of the decision is the initial categorization of the case.
An Introduction to the Law of Contract, P.S. Atiyah, 5th ed, Claredon Press, 216.