Indirect Realism and Direct Realism P1 if we were directly acquainted with external objects, then hallucinatory and veridical experiences would be subjectively distinct
P2 hallucinatory and veridical experiences are not subjectively distinct(i.e., subjectively identical)
P3 therefore, we are not directly acquainted with external objects — Ashriel
I'm not sure about P1, but P2 seems to have bigger troubles. How do you ascertain that these kinds of experiences are not subjectively distinct? Surely, in the case of hallucinations, they are intersubjectively distinct -- when someone is interacting with the world in a way we do not perceive then we reach for the explanation of "hallucination".
Being able to discriminate between reality and the imagination is a commonplace. That we can make mistakes doesn't mean that we cannot tell the experiences apart at all. If the experiences are not subjectively distinct, they certainly are intersubjectively distinct.
P1 if there is a long causal process between the object that we perceive and our perception of the object, then we do not know the object directly
P2 there is a long causal process between the object that we perceive and our perception of the object
P3 therefore, we do not know the object directly — Ashriel
P1 has to be false, I think. If there is a long causal process between the object that we perceive and our perception of the object then we are talking in a world populated by: perception, object, causes, and process. If we can talk about each of these truthfully then the only thing "indirect" here is between subject and object -- but in a way that construes reality as interacting and connected, so it's not indirect in the sense of unable to ascertain what's real.
Just because something is in aggregate -- like perception is an aggregate from the perceiver in an environment of at least a world -- doesn't mean our experience cuts us off from reality. It just means it's more complicated than two things, which given the complexity of the world shouldn't be surprising.