[ULPIANUS libro quadragensimo septimo ad Sabinum. ] §44.7.10.prNaturales obligationes non eo solo aestimantur, si actio aliqua eorum nomine competit, uerum etiam eo, si soluta pecunia repeti non possit.
[ULPIANUS, from the forty-seventh book on Sabinus.] Natural obligations are not evaluated solely by this, whether some action lies in their name, but also by this, if money once paid cannot be recovered.