In “Postscript on Qualia,” Jackson proposes that physicalism should be accepted because we shouldn’t “have opinions that outrun what is required by the best theory of those opinions’ causal origins.” In other words, one should accept physicalism as true if it has been established to be the best theory regarding its causal origin. In this case, physicalism is argued to be the best explanation for consciousness and thus should be accepted.

The knowledge argument and zombie argument both suggest that since conscious experience cannot be reduced to purely physical terms it implies that there must exist something beyond physics which explains these phenomena- aka qualia or subjective experience. However Jackson believes that by accepting a well-established physicalist account of our world we can explain certain aspects of consciousness without having to appeal to a mysterious external force.

Essentially, he argues that while it may seem impossible at first, once we accept certain facts about neuroscience/psychology and how the brain works; then it becomes easier to understand why certain mental states occur in response to our environment rather than being caused by some unknowable third entity.

Therefore, while arguments like the knowledge argument or zombie argument may appear convincing at first glance; they ultimately fail due to their reliance on an unknown source for explaining conscious experiences when better explanations exist within existing science & philosophy frameworks such as physicalism/materialism etc.