Something is objective insofar as it is independent of either a particular mind or minds altogether.

[Note: The following discussion and references are for the entries on objective, subjective, objectivity, and subjectivity.]
There are two major ways in which philosophers have construed the objective/subjective distinction: a metaphysical way and an epistemic way. These different construals concern how one would answer the following questions:
  1. What things are objective and alternatively, subjective?
  2. Are intentional states (knowledge, beliefs, mental representations, judgments, sentences, news reports) or particulars in general (rocks, trees, pains, electrons, values) objective or subjective?

The difference between the metaphysical and epistemic notions of objectivity (and subjectivity) have to do with what the bearers of the properties of objectivity (and subjectivity) are. Philosophers working on the theory of color, for instance, seem to employ a metaphysical notion of the distinction. They wonder whether colors themselves (as opposed to our judgments of them) are objective (mind-independent properties of physical objects) or subjective (mere apparent properties of objects that depend on our perceptions). In contrast, on the epistemic conception of objectivity, only judgments, beliefs, etc. are the bearers of objectivity. Thus, for instance, the judgment that the moon has no atmosphere may count as an objective judgment, whereas my judgment that vanilla is the best ice cream flavor is subjective. Many debates in the contemporary philosophy of science and epistemology that hinge on the alleged objectivity of scientific knowledge employ the epistemic notion of the objective/subjective distinction. In the philosophy of mind, it is a matter of controversy as to whether the subjectivity of consciousness (see consciousness, qualia) makes it non-physical. It is also a matter of controversy as to whether notion of subjectivity at play here is epistemic, metaphysical, or some conflation of the two (See Nagel 1986, Lycan 1996).

The epistemic notion of objectivity is itself amenable to two different construals. On the first, a judgment (or whatever) is objective just in case it purports to be about a mind independent state of affairs. On the second, a judgment (or whatever) is objective just in case there either is or can be wide spread agreement as to its truth value. Rorty (1979) calls these two different construals of objectivity, objectivity as "mirroring" and objectivity as "agreement", respectively. Gauker (1995) calls them the "correspondence" and "intersubjective" conceptions of objectivity, respectively.

No matter how you slice it, however, some notion of mind-independence versus mind-dependence is at play in distinctions between the objective and the subjective. On the metaphysical notion, something is objective just in case it exists independently of minds, and subjective otherwise. (Electrons versus feelings.) On the "correspondence" epistemic notion of objectivity, a judgment is objective just in case its truth is determined by referring to a mind independent state of affairs, and subjective otherwise. ("Electrons are negatively charged" versus "I don't care for spinach".)) On the "intersubjective" epistemic notion of objectivity, a judgment is objective just in case it is not dependent on the whims of a particular mind but requires the possibility of wide spread consensus, and subjective otherwise. ("Getting your arms pulled off without anesthesia is terrible" versus "Eating a cheeseburger without ketchup is terrible".)
Pete Mandik