He who mistakes is not considered as consenting.

Explanation

(English-origin maxim.) Consent procured through mistake is no consent — a party who agrees under a material misunderstanding of the facts has not truly consented, and the agreement may be avoided.

Where this applies

• A woman signs a contract thinking she is buying five acres when the contract actually says five square feet — her consent was based on a mistake and is not binding.
• A man agrees to pay $5,000 for a painting he believes is by a famous artist, but it turns out to be a forgery — his consent was founded on error and can be set aside.
• A buyer signs a lease thinking the rental is $500 a month when the document actually says $5,000 — the mistaken party is not considered to have truly consented.