Indirect Realism

how does an indirect realist answer the epistemological question of perception

We have (cognitively) indirect access to the way the mind-independent world around us is. We are only ever (cognitively) directly aware of the mind-dependent world of sense data. From sense data it is possible to form inferences about the existence and nature of the mind-independent world. It is always necessary to know mind-dependent sense data first, and the mind-independent second. 

how does an indirect realist answer the ontological question of perception

There exist two worlds, the mind-independent world of physical things with their properties, and the mind-dependent world of sense data. The mind-independent world is reality and the mind-dependent world of sense data are appearances. I know the mind-dependent by introspection infallibly. I have knowledge by acquaintance with the mind-dependent. I know the mind-independent by inference. This knowledge must be fallible (though it may be reasonable).

examples of secondary qualities

sound; touch; taste; colour

examples of primary qualities

size; extension; shape; number

secondary qualities

those which don’t exist in the MIO, rather arise from the interaction of the MIO and the subject of perception, they cannot be measured objectively and can only be accessed by one sense organ.

primary qualities

those which the MIO has in and of itself, they are inseparable from the MIO, objectively measurable and accessible to more than one sense organ

the four claims of indirect realism

1. there is a MIW

2. our access to the MIW is cognitively indirect,