I have long been in search of another who recognises this fact. Rocks are almost certainly staggeringly intricate beings which we are not even able to comprehend with a sane mind. Sounds strange? It's not, we're the strange ones for viewing rocks with such apathy and disinterest.

A brane is an entity. A three brane exists in three dimensions. A five brane exists in five. A thirty brane exists in thirty dimensions. This is a nice term to use with metaphysics, but because of limited human perception, it's something of an illusion. We can't tell how many dimensions something exists in, we have exactly no idea. So, we have no idea how many dimensions we exist in, or how many rocks exist in.

In fact, it's highly likely that we all exist in many more dimensions than we're aware of. Imagine being two dimensional, a stick man drawn on a sheet of paper. How would you percieve a 3d object moving past your sheet of paper? You'd see it as a series of images, one after the other, think of how a printer paints an image, line by line. This is how you'd see it. On an off-hand note, this is also how we see time. It's actually very, VERY different, but the reality is beyond our comprehension.
 So, we accept that all objects could exist in more dimensions than we are aware of, and that if an object exists in more dimensions than we can percieve, we will not see it in its entirity at any given point. What is the probability of an object existing in one dimension, but not another? Let's look at objects from 2-4 dimensions. Remember being shown a 2d shape at school? No, sorry, that was 3d. Actually, it exists in time as well, so it's four dimensional. Look around you, absolutely EVERYTHING you see is at LEAST four dimensional. And if there are more dimensions, what are the chances that anything around you is entirely seperate from any of them? Considering we know all objects we see exist in all dimensions we coprehend. It is staggeringly improbable that an object might exist entirely seperate from any dimension, so much so that the thought is absurd. Almost as absurd as the idea of rocks thinking, one might say. I would say that it is more absurd, much more.
So, what do you see when you look at a rock? You are seeing the impression of a brane which almost certainly lives in dozens (If not infinite) dimensions. You are observing the very 'tip' of an object totally beyond your comprehension. Consider this: What are the chances of an object of such mystifying intricacy, being simply inert. Dead. Without activity on any level. I'd say low. Hell, it's possible that we're making an impression on another cluster of dimensions, and some wisecracking alien being is convincing his friend that the inert object he sees is actually only a limited impression of a sentient being called a 'human'.
We should also consider thought. What is it? In humans it is the interaction between neurones in the brain. Is this the be all and end all of thought?... It seems a bit basic to me, considering the staggering array of dimensions which no doubt exist. Surely there must be many different types of thought, perhaps an unlimited amount, as we do live in an unlimited universe.

So, I ask you now, what are the chances that such a staggeringly intricate, incomprehensibly complex being, is not attached to some process, in one or more of the boggling amount of dimensions, which we might refer to as thought? I would say, non existant, which makes rock based thought a certainty.

Although they might take the term 'rock' offensively.