I think the comment refers to Descartes idea of solipsism, where we can't know the truth, because something might be beguiling our senses. From there, Descartes

I think the comment refers to Descartes idea of solipsism, where we can't know the truth, because something might be beguiling our senses. From there, Descartes derives his famous "cogito ergo sum." https://en.wikipedia.org/wiki/Cogito,_ergo_sum#Discourse_on_the_Method https://en.wikipedia.org/wiki/Cogito,_ergo_sum#Discourse_on_...