This summary of "Descartes's Basic Epistemological Argument" indicates his usage of the terms is different than a contemporary notion of objective as regardless of an observer and subjective as relative to an observer.
- Therefore, for each thinker, that of which that thinker is certain is his or her own existence as a thinking thing. [Note the important move here: each potential knower, starts from a basic foundation alleged to be known only to him or her. This is the "subjective" turn of the "modern" period in contrast to objective or "metaphysical" starting point of the Ancient philosophers.]
- Insofar as the existence of the thinking thing is indubitable, so equally indubitable is the existence of the ideas -solely as ideas- which the thinking thing is thinking. [Unfortunately the conception of the "existence" of a thing as an idea in some mind or another came to be called by the misleading label "objective reality" because it was a way of saying the thing exists as an object of thought; this leads to the strange way of speaking that if I think of something, that which I think of has 'objective reality.']
According to this article on his theory of ideas, it seems there is no "objective" in the contemporary or empirically verifiable sense of the term, and DesCartes objects are presentations made to the individual mind - like subjective "sense data" for lack of a better term:
The objective reality of a thing, on the other hand, is the reality a thing possesses in virtue of its being a representation of something
According to this article on his epistemology, the sense of "subjective" seems similar to the modern usage of objective and akin to a conflation of perspectivalism with knowledge:
If we take Descartes to be using ‘I’ to signify this subjective character ... the “I”-ness of consciousness turns out to be ... a primary datum of experience.
How did DesCartes conceive of and use the terms "objective" and "subjective"? Is his "cogito ergo sum" a representation of the subject as object?