Sentient beings have had ignorance since beginningless kalpas.

Sentient beings have had ignorance (avidyā) since beginningless kalpas; their minds have never been enlightened. If sentient beings had no ignorance—if ignorance were completely eliminated—they would be Buddhas. Sentient beings have never been Buddhas; if a sentient being had ever been a Buddha, he would never again revert to being a sentient being. This is discussed in the Sūtra of Perfect Enlightenment, where the World-Honored One gave an example: just as true gold is extracted from a gold ore, true gold will never revert to gold ore. The meaning is that after attaining Buddhahood, one will never again become a sentient being. This also shows that sentient beings have had ignorance since beginningless kalpas—there is no rationale to be given for this; it is simply such by nature. In the fourth volume of the Śūraṅgama Sūtra, Ānanda also asked the World-Honored One where ignorance comes from and why there is ignorance. The World-Honored One said that ignorance has no place of origin; it exists without any cause. If it had a cause, then it would not be ignorance.