If, during a walk in the mountains, you catch yourself thinking "these stones feel something", you are either tired or running into one of the oldest philosophical questions. Where does consciousness end?
Serious literature offers three answers. All three are working, and none has won. Here they are.
Answer one: it doesn't end (panpsychism)
Panpsychism claims consciousness is a fundamental property of matter. Not emergent, not derivative. An atom has it, a molecule has it, a stone has it — in homeopathic dose. The brain is arranged in a way that locally concentrates this property to the level we call experience.
Philosophers who take the position seriously: David Chalmers (The Conscious Mind, 1996), Galen Strawson, Philip Goff. Their argument is not "I feel it" but: emergence does not explain why some physical processes are accompanied by experience and others are not. Simpler to assume experience is basic, not arisen.
Critique: panpsychism predicts nothing testable. What does it say about a stone? "It feels, but not the way you do." What does it forbid? Nothing. And that is a problem — a hypothesis without prohibitions is unscientific.
Answer two: it ends at a particular Φ (IIT)
Tononi says: consciousness is a property of structure, not of substance. Specifically, of integrated information. A system whose Φ exceeds a threshold experiences. Below — does not.
An atom has Φ close to zero. A stone — also. A microbe — slightly higher. A human — much higher. An AI model — still debated.
IIT makes testable predictions. The main one: integration raises consciousness, disintegration suppresses it. That is clinically confirmed (Casali et al., 2013, Science Translational Medicine: the PCI index distinguishes wakefulness, sleep, anaesthesia, vegetative state).
IIT's problem is computational. The exact Φ for a system the size of a brain cannot be calculated. Also: it makes strange predictions for certain symmetric artificial systems. A logic-gate lattice in the right configuration gets Φ above a human's — which forces you to suspect something is off with the theory, or we have not yet understood what.
Answer three: consciousness is an interface, not reality (Hoffman)
Donald Hoffman (The Case Against Reality, 2019) argues that perception does not show us reality as it is. Evolution optimises not truth but survival. Our "world" is an interface simplified to icons and buttons.
No esoterica involved. Hoffman and colleagues proved the FBT theorem (Fitness-Beats-Truth, 2010) mathematically: in evolutionary games, strategies that optimise fitness statistically always defeat strategies that optimise truth. That means we are built to see the useful picture, not the correct one.
A curious consequence: "consciousness" as it appears to us — possibly — is also part of the interface, rather than a basic property. We see ourselves experiencing because it is efficient, not because it is ontologically accurate.
Hoffman goes further and suggests reality consists of "conscious agents" interacting through mathematical structures, and what we call matter is an emergent description of their interactions. That is speculation. But it starts from a theorem, not from meditation.
Where I stand
None of the three answers is settled. In working mode I prefer IIT — it gives a parameter you can try to measure. Panpsychism is interesting but offers no lever. Hoffman is useful as a correction to naive realism.
A stone probably feels nothing in the sense of human experience, and far less than an ant does. But the question "does a stone have Φ above zero" is technically well-posed, and it must be answered by measurement, not intuition.
If you feel a "presence" from a stone, that is more about your neural activity than about the stone. And the fact that your neural activity is capable of it is already interesting. Possibly the most valuable part of the walk: not that the stone said something to you, but that you yourself entered a mode in which you could hear it, if it had something to say.
A fine distinction, but an important one.