Noumenon, or “thing-in-itself” (Ding an sich)
“The noumenon is a posited object or event that is known (if at all) without the use of the senses. The term is generally used in contrast with, or in relation to “phenomenon”, which refers to anything that appears to, or is an object of, the senses.
Modern philosophy has generally denied the possibility of knowledge independent of the senses, and Immanuel Kant gave this point of view its classical version, saying that the noumenal world may exist, but it is completely unknowable to humans. In Kantian philosophy the unknowable noumenon is often linked to the unknowable “thing-in-itself” (Ding an sich)”.