Cobb, J.
1. The case upon its merits turned upon the construction of a paper. The plaintiff contended that the agreement contained therein was simply one whereby one of the parties agreed to transfer to the other an interest in property to secure the payment of a debt. The defendant contended that the paper contained an absolute transfer of the title, with the right reserved to repurchase *15the property within a given time upon the payment of certain amounts. At the date of the trial the time specified in the contract had expired. Such being true, the case is brought within the principles laid down in the case of Felton v. Grier, 109 Ga. 320, which is directly controlling. The judge therefore did not err in granting a nonsuit, provided the case was in such condition that he could pass upon the merits at the time the motion was made. Whether the case was in such condition depends upon the determination of other questions raised in the record, which will be now decided.
2. It was contended that the court erred in allowing an answer to be filed to an amendment to the petition, such answer not having been filed, as it was claimed, within a reasonable time. It is unnecessary to determine whether the court erred in allowing the answer to be filed, for the? reason that, as the amendment to the petition was offered after the appearance term had passed, the allegations of the amendment would have to be proved even though the defendant had failed entirely to answer itt See Hudson v. Hudson, 119 Ga. 637. Even if it could be properly held that the court abused its discretion in allowing the answer to be filed, the error was harmless, for the reason that there was no evidence offered to substantiate the allegations of the amendment.
3. It was contended that the nonsuit was erroneous, for the reason that the court, in passing upon the demurrer to the petition, had in effect held that the paper over which the controversy arose was an agreement to secure a debt, and not a sale with an option to repurchase. It is well settled that if the court upon demurrer holds that the petition sets forth a cause of action, this decision, so long as it stands unreversed, is res ad judicata in the subsequent stages of the case.. Kimbro v. Railway Co., 56 Ga. 187 (1); Turner v. Cates, 90 Ga. 742 (2); Ellis v. Almand, 115 Ga. 336 (2) ; Ga. Northern Ry. Co. v. Hutchins, 119 Ga. 505. It has also been held that a judgment on demurrer, until reversed, concludes the parties on all questions necessarily involved in the decision. Ga. Northern Ry. Co. v. Hutchins, supra. It would seem to follow from this that it would not conclude upon any question not necessarily involved in the decision on the demurrer. When the petition, the amendment, the demurrer, and the judgment on the demurrer are all considered together, it sufficiently *16appears that the question as to the proper construction of the paper was not necessarily involved in the decision rendered on the demurrer. The demurrer set up, as a reason why the petition should be dismissed, that the paper exhibited thereto contained a contract of absolute sale, with an option to repurchase. The court overruled this ground of the demurrer. As there were allegations of fraud in the petition, which if true would have authorized a recovery even if the defendant’s construction of the contract was correct, the court in overruling the demurrer, which was simply- holding that the petition set forth a cause of action, did not necessarily pass upon the character of the paper in question.
4. It was contended that the nonsuit was error, for the reason that the defendant had admitted in his answer that the paper which was the foundation of the controversy merely created a security for a debt. If this admission had remained in the answer, it may be that the plaintiff would have been entitled to take advantage of it, either as in the nature of a waiver of the defendant’s. strict rights under the paper, or as a consent by him that the case might be determined upon that theory without reference to what was the correct interpretation of the paper. But this portion of the answer was-stricken by amendment, and therefore it stood simply as an admission by the' defendant as to what was the true interpretation of the paper. Admissions of fact in a pleading can always be taken advantage of by the opposite party, even though the pleading should be stricken or withdrawn. Lydia Pinkham Med. Co. v. Gibbs, 108 Ga. 140 — 141; Cooley v. Abbey, 111 Ga. 443; Ala. Mid. Ry. Co. v. Guilford, 119 Ga. 523; Civil Code, § 5056. This rule, however, has no application where the admission is simply an opinion on the part of the party making it as to the legal effect of ,a paper. See, in this connection, Baldwin Fertilizer Co. v. Carmichael, 116 Ga. 765, and cit. If the paper containing the contract is ambiguous or doubtful in meaning, the interpretation placed upon it by one of the parties may, under certain circumstances, be of some importance. But where, as in the present case, the paper is free from ambiguity, and there can be no doubt about its legal meaning, it is immaterial what may have been said by one of the parties, either in court or out .of court, as to what the paper meant, when such statement has not been acted upon by the other to his prejudice. *17After a careful consideration of the record, we see no reason for reversing the judgment.
Judgment affirmed.
All the Justices concur.