If someone says publicly that he has achieved nirvana , can it be true? When you achieve nirvana , you have given up yourself. There is no person anymore. But my question is , if someone says publicly that he is arahant, is there a possibility that it can be true?
From a Theravada perspective, the answer is probably &quot;no&quot;.
While not being a sutta, the Milindapanha states if a layperson attains to Arahatship they either ordain as a monk or die.
If the layperson Arahant ordains as monk, the Vinaya forbids them making a public declaration.

Should any bhikkhu report (his own) superior human state to an unordained person, when it is factual, it is to be confessed.
Page 263

As for the Buddha &amp; monks that declared arahantship in the Pali suttas, if they used the personal pronoun &quot;I&quot;, they were only speaking in conventional language. Refer to SN 1.25.