Sankara's ontology

We start from the premise that an effect contains its cause. Oil from oil seeds doesn't appear magically. The oil already existed in the seeds. To be more precise, at least the oil-ness already existed in the seeds. The process of crushing brought it out.

There are two ways to look at this. That the oil is just another form of something that pre-existed in the form of the seeds. Or one may claim that the oil is an entirely new substance, created by the process of pressing oil seeds. Shankar argues that it's implausible to assume that the oil is different, in substance, from the oil seeds. He argues that the oil just manifests a different quality of the same substance that comprised the seeds. The substance doesn't change. It always existed. It just changed its from from that of the seeds to that of oil.

Shankar's argument in favour of a single enduring substance is a bit of sophistry. He says, reasonably, that any two forms of a substance are always related in some way. In the absence of such a relationship we couldn't reasonably claim that the two are related forms. And if we consider the two forms to be entirely different substances, then we must accord the same status to the thing that relates them. So from the two forms A and B, which we claim are different entities, we must now assume the the relationship between A and B, say Rel(A, B) is also such an entity. Obviously this regresses infinitely, since from A, B, and Rel(A, B) we must also allow for Rel(A, Rel(A, B)) and so on. Shankar claims that such an infinite regress prevents us from ever being able to explain the relationship between A and B. Since such a relationship is perceptually evident, we must assume, therefore, that, A and B are essentially the same.

Now if a cause and it's effect are just different forms of the same reality, then one may wonder where one would reach if one kept going backward from effect to cause, and further to it's own cause and so on. What remains at the beginning of this causal chain. In other words, Given the wide variety of material forms which are involved in all forms of change, what is that quality that they all share. Shankar, here, makes a bold and fairly compelling conjecture. He says they all share the quality of existence, or, simply, of existing. This is how Shankar leads to the conclusion that underlying different forms of reality that we perceive, there is but one thing that is real, and that is existence itself. It is this that Shankar calls brahm.

And to the extent that all the material forms that perceive share this underlying substance, the different forms are just perceptual layers wrapped around, the one common reality, which is brahm.

Having come this far, we may now consider whether this absolute reality, or brahm, is conscious or unconscious. We normally associate external objects as being unconscious and our own internal or mental states to be conscious. As such it is difficult to say whether absolute reality is conscious or not, since it clearly underlies all that exists - both mental and external objects or states. However, if we considers closely why we allow for the existence of different things, we can see that we allow for their existence because they are revealed to us. So they have the quality of being self-revealing. This quality is what is common between apparently external objects and mental states. Therefore, one may further argue that this aspect of being self-revealing is a quality of brahm, or absolute reality. So we have a self-revealing absolute reality at basis of all that exists. 

Shankar's argument which reaches a a contradiction by showing the existence of an infinitely expanding set is very similar to the Aristotelian third man argument. https://en.wikipedia.org/wiki/Third_man_argument