That does not, however, necessarily mean that we have to fall into imprecise poetic language when we wish to discuss the transcendental self. Like any other linguistic practice, the use of metaphor for introspective ostension can be disciplined and thereby hammered into a logico-scientific tool. At the end of the day, it may be that all that we can legitimately say about the transcendental self will be to do with its role as a boundary condition for a model of the phenomenal mind. In Samskara's Advaita Vedanta, for instance, the phenomenal world is seen as built up by superimposing layers of distinctions or 'dualties'. In set theory, the definition of any set X is equivalent to defining the extension of the set, which is to say, drawing the border line between what is in X and what isn't.
Propositional language can make statements about only the dualistic concepts that are imposed.
Hence, when we go down to the ground level, before the first dualities are imposed, we are left with the ineffable pure consciousness, which stands as a limiting case in the process of dissolving the dualistic concepts. There is an analogy with infinity in mathematics. Infinity is not a number, but a limit. Likewise, the transcendental self is not a concept but is the limit of the progression of concepts that we get by stripping away the accumulation of imposed ideas from a phenomenal experience.