Bernardo writes:
https://philpapers.org/archive/KASAOS.pdfFact 1: There are tight correlations between a person’s reported private experiences and the
observed brain activity of the person.
We know this from the study of the neural correlates of consciousness (e.g., [5]).
Fact 2: We all seem to inhabit the same universe.
After all, what other people report about their perceptions of the universe is normally consistent
with our own perceptions of it.
Fact 3: Reality normally unfolds according to patterns and regularities—that is, the laws of
nature—independent of personal volition.
Fact 4: Macroscopic physical entities can be broken down into microscopic constituent parts, such
as subatomic particles.
What makes these four particular facts significant is this: despite the formidable unresolved
problems of both physicalism [6–10] and bottom-up panpsychism [11–13], these two ontologies are
prima facie more easily reconcilable with the four facts than idealism
It is also Chapter 5 of The Idea of the World.
Facts 2 and 3 are problems for Bernardo's idealism. In Fact 2, he acknowledges the existence of a shared reality. In Fact 3, he acknowledges it works independently from personal volition.
We can look at three examples to show that the shared reality cannot be solely mental.
1- I walk with my friend to the backyard and think I see a snake. My friend says it is just a garden hose. I look more closely and realize it is a garden hose.
My perception of the hose was at variance from the shared reality of the hose. My perception was incorrect. My initial perception was different from the shared perception. The snake existed as an incorrect perception. The hose exists as a shared perception.
2- As noted in Fact 3, reality unfolds according to patterns and regularities, yet we can routinely imagine things that cannot take place in shared reality. Shared reality has a consistency that private consciousness does not require.
I can imagine throwing a ball into the air and having it fly into outer space. In shared reality, the ball would fall back to earth.
Thrown balls consistently return to earth in shared reality. They are not required to do so in consciousness.
3- Shared reality can produce effects that can be perceived by myself and others. My consciousness can produce effects that can only be perceived privately.
I can hit my hand with an imaginary hammer but no one else will see or feel the effects. If I hit it with a shared reality hammer, other people and I can both see the effects.
4- The shared world is different from my consciousness of it. The shared world does not have the characteristics of consciousness.
Idealism cannot be correct. Shared reality differs in quality from purely mental reality.