Consciousness as the ability to observe refers to the phenomenon of consciousness not its function (Block, 1995), so being conscious doesn’t require any sense, thought or feeling. Damage to the visual cortex causes blindness but it doesn’t stop consciousness, as people with locked in syndrome are conscious, and people born with no cortex are conscious (Merker, 2007) so it can’t be a cortical area. No brain area has been identified as the seat of consciousness, as it persists even when the cerebellum, amygdala, hippocampi or cortex fail. The ability to observe is just there in a way that doesn’t require any particular brain function. It can apply to any sense, memory or feeling so James concluded in 1892 that consciousness is a fundamental fact:
“The first and foremost concrete fact which everyone will affirm to belongs to his inner experience is the fact that consciousness of some sort goes on.” (James, 2019)
In scientific terms, this fact is valid because anyone can confirm that they observe and it is reliable because others can repeat the experience. That we each observe differently is irrelevant to the fact that we do observe. Separating what is known from what is assumed, we truly know that we observe phenomena but not what really exists (Kant, 2002). I know that I observe but I assume a physical world out there. All I know with absolute certainty is that I observe reality, and everything else is just assumption, or as science says, theory.
Even in physics, both relativity and quantum theory require an observer. The observer defines the reference frame in relativity and in quantum theory, collapses the quantum waves that cause every physical event. In our lives, the first fact we know about reality is that we observe it. Without an observer there is no first person, so we would say “It is red” not “I see red”. To say I see or I hear implies an observer. That we observe is the first fact because there are no other facts without it.