A remarkably large number of Renaissance artists were illegitimate, including Alberti and Ghiberti. For them, as for Leonardo, this was both a curse and a blessing. Had he been born "legitimately," Leonardo would likely have followed in his father's footsteps and become a notary or a lawyer. But those professions' guilds refused entry to illegitimate children. Leonardo couldn't become a doctor or a pharmacist, nor could he attend university. By age thirteen, most doors were already closed to him.