A rule of interpretation that a judge, called upon to interpret an otherise unclear legal document (such as a will), shall take into account the circumstances in which the document was created.
In Dobson Estate v. Dobson, 2000, published at 32 Estates & Trusts Reports, 2nd Series, page 62, the Ontario Superior Court of Justice, Justice O'Connor presiding, stated:
"Where the testator's intention cannot be ascertained from the plain meaning of the words used the court may consider the surrounding circumstances known to the testator when he made his will -- the so-called Armchair rule. That is, the court may sit in the armchair of the testator, assume the knowledge he had of the extent his assets, the size and makeup of his family and his relationship to its members, so far as such things can be ascertained by the evidence."