Harman’s OOO is rarely stated without a deceptive rhetorical wrapping, but its principle ideas lead to extremely unacceptable consequences.
Everything we perceive and know is illusion. In particular, time is an illusion. Literature, science, common sense are all a dream. History is a dream. Change is a dream. Real change is impossible.
Objects cannot be distinguished by any known, perceived, or imaginable property or relation.
Objects withdraw from relation. Mathematical relations are no exception. Objects are non-relational. Difference is no exception, not even bare numerical difference.
There is only one object (in a non-relational, and therefore non-numerical sense of “one”).
This object is cognized by intellectual intuition, its very existence a bold conjecture, in plain words an unsupported guess. The conjecture cannot be supported, there is no referential and no inferential relation going from the unreal to the real, as the real is non-relational (“withdrawn”).