Contract; vitiating circumstances; common mistake; objective unconditional agreement.
Facts: Leaf saw a painting of Salisbury Cathedral that International Galleries had for sale. Leaf offered to buy this painting. When he bought it, both Leaf and the seller believed the painting was the work of famous artist John Constable. After buying it, Leaf discovered that the painting had been done by another artist. Leaf wanted the sale made void on the grounds that both he and the seller had been mistaken about who had done the painting.
Issue: Could the contract be avoided on grounds of the parties' mistaken belief that the painting was the work of John Constable?
Decision: In the circumstances, the mistake did not justify setting the contract aside as void.
Reason: Basing the decision on the objective facts of the case, it was clear that the subject matter of the contract was agreed simply as 'this painting of Salisbury Cathedral'. There was no objective evidence that the agreement had been for 'a painting by John Constable'. Thus the error as to the artist was irrelevant and the contract was binding despite the common error. Put another way, the agreement between Leaf and International Galleries was not objectively conditional on the truth of their belief that the artwork was painted by John Constable.