المعنى الاصطلاحي

They are those who deny the established facts and claim that facts are subservient to beliefs.

الشرح المختصر

"Al-‘Indiyyah" is one of the sects of sophistic philosophers who were known for their excessive indulging in argumentation and manipulation of words and facts. They believe that the reality of things are subject to beliefs, hence, whoever holds a certain belief about something, then it is, in reality, as he believes it to be. This entails that things have no fixed intrinsic reality; rather, reality is a matter that is subservient to perception. Thus, if someone believes something to be "jawhar" (essence), then it is as such; and if someone believes it to be "qadeem" (eternal, has no beginning), then it is as such; and if he believes it to be "hādith" (opposite of "qadeem"/has a beginning/created), then it is as such; and so on. Undoubtedly, this claim is false, as dictated by sense and reason.

التعريف اللغوي المختصر

"‘Indiyyah": withness; ascription to "‘inda" (with/at), which expresses the present place of something. "‘Indiyyah" describes the state of something as being with something else or at its place. Other meanings: nearness/proximity, being described with something, possession, specialization.