[IDEM libro quarto ad Sabinum. ] §28.5.4.prSuus quoque heres sub condicione heres potest institui: sed excipiendus est filius, quia non sub omni condicione institui potest.
A self-successor (suus heres) also can be instituted heir under a condition; but a son must be excepted, because he cannot be instituted under every condition.
et quidem sub ea condicione, quae est in potestate ipsius, potest: de hoc enim inter omnes constat.
And indeed, he can be instituted under that condition which is in his own power; for on this point there is agreement among all.
sed utrum ita demum institutio effectum habeat, si paruerit condicioni, an et si non paruerit et decessit? Iulianus putat filium sub eiusmodi condicione institutum etiam, si condicioni non paruerit, summotum esse, et ideo si coheredem habeat ita institutus, non debere eum exspectare, donec condicioni pareat filius, cum et si patrem intestatum faceret non parendo condicioni, procul dubio exspectare deberet.
But does the institution have effect only if he complies with the condition, or also if he does not comply and has died? Julian thinks that a son instituted under a condition of this kind is excluded, even if he does not comply with the condition; and therefore, if he who is thus instituted has a co-heir, the co-heir ought not to wait until the son complies with the condition, although, if the son were to make the father intestate by not complying with the condition, the co-heir undoubtedly ought to wait.
quae sententia probabilis mihi uidetur, ut sub ea condicione institutus, quae in arbitrio eius sit, patrem intestatum non faciat.
This opinion seems to me acceptable, namely, that one instituted under a condition which is in his own discretion does not make the father intestate.
§28.5.4.1Puto recte generaliter definiri: utrum in potestate fuerit condicio an non fuerit, facti potestas est: potest enim et haec 'si Alexandriam peruenerit' non esse in arbitrio per hiemis condicionem: potest et esse, si ei, qui a primo miliario Alexandriae agit, fuit imposita: potest et haec 'si decem Titio dederit' esse in difficili, si Titius peregrinetur longinquo itinere: propter quae ad generalem definitionem recurrendum est.
I think it is correctly defined in a general way: whether a condition was in one's power or not is a power of fact. For even this condition, 'if he shall have reached Alexandria,' can fail to be in one's discretion due to winter conditions; and it can be in one's power if it was imposed on one who is active at the first milestone from Alexandria. Also, this condition, 'if he shall have given ten to Titius,' can be difficult if Titius is traveling on a distant journey; because of which we must recur to the general definition.
§28.5.4.2Sed et si filio sub condicione, quae in eius potestate est, herede instituto nepos sit substitutus siue extraneus, puto uiuo filio non exstaturum heredem substitutum, post mortem uero exstaturum, nec necessariam a substituto filii exheredationem, cum et, si fuerit facta, frustra est: post mortem enim filii facta est, quam inutilem esse alias ostendimus: opinamur igitur filium, si sit institutus sub ea condicione et sit in eius potestate, non indigere exheredatione a sequentibus gradibus: alioquin et a coherede indigebit.
But even if, a son having been instituted heir under a condition which is in his power, a grandson or an outsider is substituted, I think that while the son is alive the substituted heir will not emerge, but after his death he will emerge; nor is a disinheritance of the son by the substitute necessary, since even if it has been made, it is in vain; for it was made after the death of the son, which we have shown elsewhere to be useless. Therefore, we think that the son, if he is instituted under that condition and it is in his power, does not need disinheritance by the subsequent degrees; otherwise, he will also need it from a co-heir.