Sophist
I figured you meant Plato- I think I need to go over his stuff again. I don't see why having a "perfect" conception of something necessitates its existence in an "objective" sense, although lately I'm wondering if that's even really necessary to have a valid perspective on "reality."
Conceptual vs actualized concepts.
A concept is only perfect so long as it is not actualized. When something leaves the world of concepts and becomes what is regarded as a physical reality, it becomes subject to the vaguerities of that environment.
Omniscience is required to have a complete and perfect perspective. However, this does not prevent us from having what might be called a working understanding. So a perspective, while far from complete, may be equally valid with other perspectives which are also far from complete.
Without utterly divorcing ourselves from our senses and the way they influence our thought, we will not be able to attain a truely objective perspective. As we are the originating point for our own observations, even the observations about other people's observations, we are unlikely to attain more than theoretical objectivism.