Harman argues for a flat ontology, in which all objects (of the mind) are on equal footing. Here is his list of examples of things (of the mind) which are real — Sherlock Holmes, real humans and animals, chemicals, hallucinations.
Delanda pointed out in that a realist does not necessarily mean one is a default materialist in The Rise of Realism (co-spoken with Harman). What Delanda had meant was materialists take physical objects as what is real. Harman’s position is that objects of the mind are real.
I side with materialists here and treat all physical objects as the only real objects. But equally I treat physical objects on equal footing with equal value. It is only the mind (the perception, conceptualisation and symbolisation) that give various values of things. It is something we do as a sentient/perceptient being. To step away from it is to “deny” (to project the possibly of suspended judgment with perception, conceptualisation and symbolisation) the reality of this being.
In this conception (which is an object of the mind, and not a real thing) the conception of an object of the mind a process of a thing. It marks the reality (things, space and time) of a thing but exists not in itself as a thing.