I like Kant’s arguments about thought and noumenal things-in-themselves because they advance analytical thought about the knower and known. One has a way to address Descartes’ criterion with the Critique of Pure Reason, and that works even while people are advancing experimental and technical learning about the world scientifically. Empiricism arose to explain why objective material things and statements about them are meaningful before W.V.O. Quine explained that all propositions and thought about external objects are made with inward, intentional thought.
The idea that extensional thought exists that has a direct relation to ‘objective reality’ is logically unsupportable. Perhaps it isn’t entirely unsupportable though. For if nature has no words in it for-itself, other people than oneself do at least. The presence of words that are rational and responsive in others supports the idea of objective reality directly in my opinion. Even so people conversing may share common illusions for shared propositions made about external reality with compatible dialectics.
What reality is of course remains conditional and subjective although something objective including rational people does certainly exist (unless nature has some kind of great artificial intelligence trickery going on and all people besides myself are emanations from it.
Those idealist arguments about God or a Quantum computer creating reality for sentient minds to experience, or the idea that everything that exists is an idea of God including sentient human minds as subroutines in the thought of God are still viable, however the presence of rational sentient intelligence besides oneself supports directly the proposition that some objective intelligence or objective reality does exist-whatever it is for-itself and in-itself though unknown to oneself.