The word _noumenon_ has not become naturalized in our language, and did not exist in Greek.[96] It can convey no intelligible meaning to common readers without tracing its derivation, and when it is analyzed we can attribute to it no meaning but a purely arbitrary one, even if we can arrive at that arbitrary signification. In fact, it is a word made by and for the school of Kant. Its first syllable is the Greek noun νοῦς or νόος, which corresponds to our English word _thought_ or _intelligence_. The Greek verb νοέω, _to think_, was primarily used as _I perceive_; the act of the mind in seeing. This idea was distinct from εἴδω, which conveyed the plain meaning of I _see_. But so subtile were the Greeks in their use of words, that εἴδω was sometimes used specifically to mean _to see with the mind's eye_, or, as we sometimes say, to _realize_, or to have a mental perception of. In the Greek use of the two words νοεω and εἴδω, no distinction was made between _phenomenon_ and _noumenon_. To a cultivated Greek, _phenomenon_ would mean something perceived, and _noumenon_, if he had possessed the word, would have had the same meaning. He would have used the two words interchangeably, to express either sight by the visual organs or mental perception. Mr. Spencer uses them as if they meant different things, as if _phenomenon_ were something different from _noumenon_. But _noumenon_, according to its derivation (for it is coined as the participle of nοεων), means a thing, subject, or object, _perceived by the mind_. The root idea is mind-action, the verb νοεω meaning to do what the mind does in apprehending a subject or object. So that the derivation of _noumenon_ does not help us to understand the Kantian or Spencerian use of the word. As this use of the word is, then, purely arbitrary, we must try to understand, as well as we can, what this arbitrary meaning is. As well as I can fathom it, in contrast with _phenomenon_, the meaning is that _phenomenon_ is something that we see, and _noumenon_ is the ghost or double of what we see. We see a thing with our eyes; but our mind does not see it--it perceives its ghostly double. This is _noumenon_. Penetrating, or trying to penetrate, a little further into Mr. Spencer's meaning, it would seem that when he says that _phenomenon_ without _noumenon_ is unthinkable, he means that, although we can see a thing with our corporeal eye, we can not think of it without the mental act of seeing its image with the mind's eye; and then he adds that _noumenon_ can not be thought of in the true sense of thinking, because _noumenon_ is an abstraction or a mere ghost of a subject or an object.