1Paulus, On the Edict, Book XLIV. Ignorance is either of fact or of law. 1For where anyone is not aware that he to the possession of whose property he is entitled is dead, time does not run against him. Where, indeed, he is aware that his relative is dead, but he does not know that his estate belongs to him on account of his being the next of kin, or, where he is aware that he has been appointed an heir, but does not know that the Prætor grants the possession of the property of a deceased person to those who have been appointed his heirs; time will run against him because he is mistaken with respect to the law. The same rule applies where the brother of the deceased thinks that his mother has the preference. 2If anyone does not know that he is related to the deceased, sometimes he is mistaken concerning the law, and sometimes with reference to the fact; for if he is aware that he is free, and who his parents were, but does not know that he is entitled to the rights of relationship, he is mistaken as to the law. Where anyone who is a foundling does not know who his parents are, and serves another as a slave, thinking that he himself is a slave, he is mistaken rather as to the fact than as to the law. 3Moreover, where anyone knows that another is entitled to the possession of the property of an estate, but does not know that the time during which he should have taken possession of the same has elapsed, he is mistaken as to the fact. The same rule applies where he thinks that he has obtained possession of the property. Where, however, he knows that he has not claimed the estate, and that he has allowed the time to elapse, but is ignorant that he is entitled to the possession of the property on the ground of succession, time will run against him because he is mistaken with respect to the law. 4We hold the same where a man is appointed heir to an entire estate, but does not think that he has a right to demand possession of the same before the will is opened; but if he is ignorant that there is a will, he will be mistaken with reference to the fact.

2Neratius, Parchments, Book V. Error in law should not, in every instance, be considered to correspond with ignorance of the fact; since the law can, and should be definitely settled, but the interpretation of the fact very frequently deceives even the wisest men.

3Pomponius, On Sabinus, Book III. There is a great deal of difference whether anyone is not informed regarding the case and acts of another, or whether he is ignorant of the law which affects himself. 1Cassius states that Sabinus holds that it should be understood that ignorance, in this instance, does not refer to a person of abandoned character, or to one who, through negligence, thinks himself secure.

4The Same, On Sabinus, Book XIII. It is denied that ignorance of the law is of any advantage in usucaption, but it is established that ignorance of fact is a benefit.

5Terentius Clemens, On the Lex Julia et Papia, Book II. It seems to be most unjust that knowledge should injure another rather than its possessor, or that the ignorance of one person should profit another.

6Ulpianus, On the Lex Julia et Papia, Book XVIII. Neither gross ignorance of the facts should be tolerated, nor scrupulous inquiry be exacted, but such knowledge should be demanded that neither excessive negligence, too great unconcern, nor the inquisitiveness that characterizes informers may be exhibited.

7Papinianus, Questions, Book XIX. Ignorance of the law is not advantageous to those who desire to acquire it, but it does not injure those who demand their rights.

8The Same, Definitions, Book I. An error of fact does not, indeed, prejudice the rights of men where they seek to obtain property, or to avoid losing it; and ignorance of the law is no advantage, even to women, when they attempt to acquire it. A mistake in law, however, does not injure any person in an attempt to avoid the loss of property.

9Paulus, On Ignorance of Law and Fact. The ordinary rule is, that ignorance of law injures anyone, but ignorance of fact does not. Therefore, let us examine to what instances this rule is applicable, for it may be stated, in the first place, that minors under twenty-five years of age are permitted to be ignorant of the law; and this also is held with respect to women in certain cases, on account of the weakness of the sex; hence, so long as no crime has been committed, but only ignorance of the law is involved, their rights are not prejudiced. On the same principle, if a minor under the age of twenty-five lends money to a son under his father’s control, relief is granted him, just as if he had not lent the money to a son subject to paternal authority. 1Where a son under paternal control, who is a soldier, is appointed heir by a comrade-in-arms, and does not know that he can enter upon the estate without the permission of his father, he can ignore the law in accordance with the Imperial Constitution; and therefore the time prescribed for the acceptance of the estate does not run against him. 2Ignorance of the fact, however, does not injure anyone unless he should be guilty of gross negligence; for example, what if every one in the town knew what he alone does not? Labeo very properly says that neither the knowledge of the most inquisitive, or the most negligent man, should be understood to be meant, but that of him who can obtain it by diligent inquiry. 3Labeo, however, thinks that ignorance of the law ought not to be considered excusable unless the party should not have access to a magistrate, or is not intelligent enough to easily ascertain that ignorance of the law is a detriment to him, which is very rarely the case. 4Where anyone does not know that the vendor is the owner of the property sold, more attention should be paid to the transaction itself than to the opinion of the purchaser; and therefore, although he may believe that he bought the property from someone who was not its owner, still, if it is delivered to him by the owner, it will belong to him. 5Where a party who is ignorant of the law does not avail himself of the Lex Falcidia, a Rescript of the Divine Pius says that his rights will be prejudiced. Moreover, the Emperors Severus and Antoninus stated the following in a Rescript, namely: “Where, in discharging a trust, money is paid which is not due, it cannot be recovered, unless it was paid by mistake. Wherefore, the heirs of Cargilianus, when they paid over money left by will for the purpose of building an aqueduct for the Republic of Cirta, not only did not require the bonds which are usually executed to compel the repayment by municipalities of any excess which they might receive above what was permitted by the Lex Falcidia; but they even stipulated that the said sum of money should not be applied to any other purpose, and knowingly and deliberately suffered the said money to be used for the construction of the aqueduct, hence they had no right to demand that anything should be returned to them by the Republic of Cirta, on the ground that they paid more than was due; since there would be injustice on both sides, for the money to be recovered which had been given for the purpose of building an aqueduct, and for the Republic to be compelled to pay out of the funds belonging to it for a work which entirely represented the glory derived from the liberality of another. “If, however, the heirs thought that the claim for the recovery of said money was well founded, for the reason that they failed, through lack of information, to profit by the provisions of the Lex Falcidia, they should know that ignorance of fact would be of advantage to them, but ignorance of law would not; and that relief is granted, not to fools, but to those who are honestly mistaken with reference to the facts.” 6Although municipalities are mentioned in this Rescript, still, the same rule should be observed with reference to all kinds of persons. And while, in the case stated, mention is made of money left for the purpose of constructing an aqueduct, in this instance alone it must be held that an action for its recovery will not lie, for the beginning of this constitution is of general application, as it shows that if, through mistake, the trust was not discharged, any money paid which is not due cannot be recovered. Moreover, that section is also of general application which sets forth that parties are not entitled to recover who, through ignorance of the law, did not avail themselves of the benefit of the Lex Falcidia; and, according to this, it can be stated that if money which was left in trust and had been paid, had not been left for some specified purpose, even though it had not been expended but remained in the hands of the person to whom it was paid, an action to recover it will not lie.

10Ad Dig. 22,6,10BOHGE, Bd. 1 (1871), S. 114: Die Rechte unbevormundeter Pflegebefohlnen können durch ihre Handlungen oder Unterlassungen nicht verwirkt werden.Papinianus, Opinions, Book VI. Youths who have not arrived at puberty and act without the authority of their guardians are not considered to know anything.