The space-time, subject-object phenomenal universe is a manifestation of mind, of which day and sleep dreaming are examples in a second degree.
The result of this individualisation process, based on seriality, which all degrees of dreamers know as 'reality', has no objective resemblance to that which causes it to appear, because that which causes it to appear has no objective quality at all.
Therefore that is totally inaccessible to any form of objective cognition, let alone of description. The only words that can indicate it at all are This, Here, Now, and Am, and in a context which is entirely abstract.
The negative method is provisional only; it turns from the positive to its counterpart, and then negates both. That wipes out everything objective and leaves an emptiness which represents fullness, total absence which represents total presence. Here the thinking (and not-thinking) process ends, and the absence itself of that IS the Inconceivable.
Inconceivable for whoever attempts to conceive it. But who suggested that we should do that?