Section 18

the positive assertion, in a manner not warranted by the information of the person making it, of that which is not true, though he believes it to be true;

any breach of duty which, without an intent to deceive, gives an advantage to the person committing it, or anyone claiming under him, by misleading another to his prejudice, or to the prejudice of anyone claiming under him; and

causing, however innocently, a party to an agreement to make a mistake as to the substance of the thing which is the subject of the agreement.

Voidability of agreements without free consent