The phenomenal is conceptual - appearance or form, the interdependent counterpart of which is the non-phenomenal, which is also conceptual - non-appearance or formlessness.

The source of the phenomenal and the non-phenomenal ('the world of form and the formless world' as the Masters referred to them) is noumenon.

'Noumenon', therefore, is not the interdependent counterpart (or the opposite) of 'phenomenon' but the source of 'phenomena and of non-phenomena'. All this is purely conceptual.

Phenomena are both positive and negative, both appearance and non-appearance, form and non-form, both presence and absence of form or of appearance, for each is dependent on the other and can have no hypothetical existence apart from the hypothetical existence of the other.

'Noumenon' is a symbol indicating double phenomenal absence - the absence of both counterparts or, as sometimes expressed, the absence of the negative counterpart (a double absence), which is also the absence of the absence of the positive.

Even as such, philosophically speaking, 'noumenon' still appears to be dualistic; that is, to be an objective concept requiring a 'cogniser' of some 'thing cognised'. But here there is no thing cognisable, and precisely because 'it' (noumenon) is also the cogniser, and indeed all hypothetical cognisers that ever were or ever could be.

As such 'it' is unfindable, unknowable, simply because 'it' could not be as an object of anything but 'itself' and 'it' could never know 'itself' as an object, so that the symbol is just a phenomenal ruse contrived in order to indicate some 'thing' which is not such. Referring to 'it' as 'Suchness' or 'Tao', or in any other way whatever, is equally futile logically - since 'it' is the supposed cognising element, the supposedly cognised, and the apparent act of cognition.