Say the ratio out loud before you open Reasoning — recalling it unprompted is exactly what the exam pays for.
Why it matters
It is cited in this paper for one proposition, and a precise one: the rule against merger for foreign judgments outlived the reason for its existence. It is a short chapter, and an honest one — the course gives the observation, not the facts.
Facts
This course cites the case for Lord Wilberforce's observation on non-merger and does not set out its facts.
Held
The survival of non-merger, after its rationale had died, is an illogical survival whose continued existence is precarious.
Reasoning
Step one — state the domestic rule that is being contrasted. In domestic English law a plaintiff who obtains judgment cannot sue again on the original cause of action: it merges in the judgment.
Step two — state the exception for foreign judgments. A creditor holding a foreign judgment may either sue in England on the foreign judgment, or bring an action on the debt, in which case the foreign judgment may be used only as evidence of the debt.
Step three — identify the vanished rationale. The exception rested on the older view that a foreign judgment was mere evidence, re-examinable on the merits. Godard v. Gray killed that view. Once a foreign judgment became conclusive, the reason for denying it the merging effect of a domestic judgment disappeared.
Step four — hence the description. What is left is a rule without a reason, surviving on inertia.
Exam use
It opens: Explain the doctrine of obligation and the rule against merger — as the critical observation that completes the account.
Show that the anomaly is not merely English. The Indian scheme reproduces it in statutory dress: where the territory is not reciprocating, the decree-holder must file a suit on the foreign decree, or on the original cause of action, or both, and may execute only the resulting domestic decree — Marine Geotechniques v. Coastal Marine Construction & Engineering Ltd., with a limitation of three years from the date of the foreign judgment or decree. The option that non-merger preserves is written into the Indian rule.
Use it in an essay on the basis of enforcement. Comity was abandoned because it made enforcement turn on reciprocity and left almost no room for defences; obligation replaced it, eliminating reciprocity and making the defences principled, since any ground that negatives the obligation may be pleaded. Non-merger is the one loose thread the change left behind.
It does not decide that non-merger has been abolished; it records that it is anomalous and insecure.