Once we use intersubjectivity and we agree on the terms, it is possible to form objective judgments. For instance, say we subjectively decide "wrongs" are punishable in some form. Say we both subjectively agree theft is a "wrong." We can then objectively conclude theft is punishable in some form. As long as the subjective definitions of "wrongs" as punishable offenses and theft as a "wrong" stay the same, the objective conclusion that theft is a punishable offense also remains true.

Take the brain in the vat example. You must either make the subjective decision that what you see is reality and you're not a brain in a vat or not. If you make the subjective decision that what you see is reality then you can make objective decisions about that reality - that killing yourself or others would end your or their perception of reality and that you or they would, in reality, be dead.