I'm not sure if this is your area:
But I am trying to understand shopenhauer's idea that our perception makes up what we experince but we cannot know "things in themselves" directly. I have been listening to Bryan Magee talking to Fredrick Coppleston about shaupenhaur but cannot follow when they say that the noumenon is all one and beyond time space and causality.
Can you throw some light on why things in themselves is not possible as it is only thing in itself not multiplicity or plural?
sorry not not explaining the question clearly
ANSWER: No need to apologize; you expressed the question perfectly.
The idea about our perceptions as "forms of intuition" that give us a picture of the world that is not necessarily reality is due to Kant, one of Schopenhauer's predecessors. Kant came up with the idea as a means of resolving "antinomies" -- contradictions -- in reasoning, most of which are now understood not to be contradictions at all.
Kant thought that space, time, causation, etc., were all means by which the human mind interpreted reality -- they were not reality itself. A red apple held in my right hand at 9:50 PM (EDT) on August 20, 2013 (CE)is not what-an-apple-really-is. It's the perception of what-an-apple-really-is that my brain and nervous system can give me. What-the-apple-really-is is the thing in itself, which we cannot know.
Kant called what we CAN grasp with our senses "phenomenal." Everything else is "noumenal" and can be grasped, it at all, only through reason (Schopenhauer, for somewhat unclear reasons, thought that music worked too.)
Since space, time, and causality are "forms of our intuition", the noumenal is not "in" space or time and is not subject to causality. Oneness is another question. Kant had a problem here since numbers are graspable only by reason, hence noumenal, but where there is no "principle of individuation" we cannot determine whether there are one of many nouemenal objects of certain types.
A bit of reasoning that Kant did not get to is this: phenomenally you and I are clearly two different selves, but are we different noumentally? Kant could see no way to tell.
The German Idealists (Hegel, etc.0 weren't afraid to draw the conclusion that, there being no principle of individual selves, there could be only one. (Which Hegel called Spirit...)
And so Idealism was off and running, and dominated philosophy for about 100 years.
Hope this helps.
---------- FOLLOW-UP ----------
QUESTION: Thanks Charlie
I am missing something somewhere in my reasoning.
I think schopenauer thought that Kant had missed something in his failure to access noumenon - that we, individually have some extra access that doesn't necessarily come to us through our senses which is the internal experience we have of our individual internal selves. But I still don't see that our internal experience gets us much clser to noumenon as we are still processing our internal experiences presumably through the matter of the brain in some way and our intellect is a product of our senses to some extent.
The real issue I have is that if each object we perceive has an underlying essence or thing in itself why is it unity and not multiple incidents of objects - this sound more like Plato's forms.
I suppose what I am trying to get to is if noumenon in unmanifest and not individual objects how can they be described as things in themselves when they must be undifferentiated, unlimited, substance? Is it like noumenon is putty and we carve our percieved objects out of it ?
Magee and coppleston seemed to say it was self evident that noumenon was all one. The only way I can see that is that it doesn't occupy space so how does it form the individual objects we perceive?
NOt sure I am making sense.
Your first paragraph explains why Schopenhauer was wrong. Good job!
Just as there is no "principle of individuation of noumenal selves" -- at least, not one known to us -- there is no principle of individuation of noumenal anything. It might well be the case that instead of as many apples-in-themselves as there are perceived apples, it might be the case that there is only one noumenal apple. We simply cannot know. If there is only one noumenal apple, it would indeed be like a Platonic form.
There might be one and only one noumenal thing that we perceive as a myriad of different things. Hegel thought so.
As for the space issue, remember that space itself is a "form of intuition"; it makes us think that noumenal objects have to take up space, but as neoumena, they are outside of time and space. They're logical objects.
Hope this helps.