# *Mater semper certa est* > In Roman law, mater semper certa est (from Latin: “the mother is always certain”) is a legal principle which has the power of praesumptio iuris et de iure (“presumption of law and by law”), meaning that no counter-evidence can be made against this principle. It provides that the mother of the child is conclusively established, from the moment of birth, by the mother’s role in the birth.[^1] > The Roman law principle, however, does not stop at the mother, in fact it continues with *pater semper incertus est* (“The father is always uncertain”).[^2] [^1]: ‘Mater semper certa est’, *Wikipedia*, updated 28 June 2024, https://en.wikipedia.org/wiki/Mater_semper_certa_est. [^2]: ‘Mater semper certa est’, *Wikipedia*, updated 28 June 2024, https://en.wikipedia.org/wiki/Mater_semper_certa_est.