De transactionibus axiomata

LXXXVII.
But if a settlement has been made concerning several distinct causes or points at once, a falsehood that gave rise to a settlement regarding one point is not carried over to another point, such that the settlement would be rescinded in its entirety.

LXXXVIII.
A settlement is also rescinded if it pleases those who have settled between themselves that they should depart from the settlement.

LXXXIX.
And it is truer that this holds not only while the matter is still untouched, but even if the settlement has been fulfilled on one side, provided that then, with everything paid for the sake of the settlement being restored, it may be retracted by the consent of both parties settling.

XC.
However, under the pretext that the one who regrets the settlement claims that he settled while sick, the laws do not allow a settlement to be rescinded if there is no other defect; since in matters that are carried out by consent, the integrity of the mind alone, not the health of the body, is required from those who must consent, given that we consent not with the body, but with the mind.

XCI.
Likewise, the fact that a settlement is said to have been made at night is not sufficient to rescind a settlement entered into in good faith.

XCII.
In the same way, a settlement is not retracted because a writing did not intervene, for the substance of a settlement consists not in writing, but in consent.

XCIII.
But even if the cause for which the settlement is said to have been made has not followed, it is not therefore always permitted to depart from the settlement if the other party is unwilling.