he common essence of all these theories, in shortLis that what is known is antecedent to the mental act of observation and inquiry, and is totally unaffected by these actsj otherwise it would not be fixed and unchangeable. This negative condition, that the processes of search, investigation, reflection, involved in knowledge relate to something having prior being, fixes once for all the main characters attributed to mind, and to the organs of knowing. They must be outside what is known, so as not to interact in any way with the object to be known.