The defendant does not claim that any fraud or duress was practiced upon him or that he signed the order by mistake or did not notice its provisions. On the contrary, his testimony shows that he knew the order contradicted the oral conversations previously had as testified by him and still he signed and delivered it to plaintiff’s agent to be sent to plaintiff. It was sent as intended. It was accepted and acted upon by plaintiff as written. It purported to express all the agreements and in plain terms negatived the existence of any conditions not expressed therein. It was declared -irrevocable and was to become operative immediately and unconditionally upon acceptance and not upon the happening of some future event, condition, or notice.
Upon the acceptance of the order and the delivery of the books to the defendant the plaiiitiff became entitled to recover the stipulated purchase price. Fountain City D. Co. v. Peterson, 126 Wis. 512, 106 N. W. 17.
The parol testimony admitted materially changed the written contract by making it conditional instead of absolute, and by incorporating conditions expressly negatived in the writing itself. Written contracts cannot be so contradicted by parol testimony. Borchert v. Skidmore L. Co., ante, p. 523, *581171 N. W. 70, and authorities cited. The parol testimony was erroneously admitted.
Counsel for defendant calls our attention to the rule of law that permits the entire contract to be shown though a part of it rests in parol. That rule is operative only when there is no vital contradiction between what is expressed in the writing and the oral agreement. But this contract says it is entire. To prove the contrary would be to contradict the writing. We are also reminded that it may be shown by parol testimony that an instrument was given on condition and that such condition has not been satisfied. No doubt such is the rule as to writings that are consistent with such proof. But this instrument says it is irrevocable and that no conditions exist not expressed therein. And finally it is urged that a collateral agreement which was the inducement for entering into the written contract may be shown by parol. No doubt it may in a proper case. But not where the written contract expressly negatives any collateral agreement, and no claim is made that the signature thereto' was obtained by reason of duress, fraud, mistake, or excusable neglect.
The law seeks to protect both parties to a written contract. Hence, when a writing speaks plainly and declares itself to be the entire contract, and is complete in itself; when it negatives prior or contemporaneous oral agreements ; when it says there are no conditions existing not expressed therein, and that it is irrevocable, it must be held to contain the entire agreement between the parties or else written contracts would become mere scraps of paper subject to the same infirmities of self-interest, forgetfulness, and misunderstanding that attend oral agreements. It is for the purpose of avoiding these infirmities that written contracts are entered into, and it is in the furtherance of justice and honesty that the law declares that what a man has plainly asserted under his own signature he should not be permitted to deny except upon proof of duress, fraud, mis*582take, excusable neglect, or some other adequate cause. We have no' such case here.
By the Court. — Judgment reversed, and cause remanded with directions to enter judgment dismissing defendant’s counterclaim upon the merits and to: enter judgment for plaintiff upon its cause of action in the sum of $51.50 and costs as of March 8, 1918.