{ 1 } - facts about our sensations can be evidence for beliefs about external objects.
{ 2 } - we have no knowledge of external objects.
{ 3 } - statements about external objects can be translated into statements about our sensations.

Critical cognitivists admit that we can't DEDUCE the existence of external objects from facts about our sensations. But they contend that facts about our sensations can make beliefs about external objects reasonable or evident.

This is Chisholm's view. He appeals to principles of evidence like "If you think that you're seeing a external object, then, unless you have positive reason to doubt your perceptions, it's reasonable for you to believe that you're seeing an actual object."