I am reading The One and the Many by W. Norris Clarke, SJ, a book on Thomistic metaphysics.
In Ch.2 (p.36-37), Father Clarke characterizes the relationship between the objective and the subjective in this manner:
"Ancient philosophers tended to look on the world from an impersonal, objective viewpoint, as a kind of spectacle spread out before them, outside of them, so to speak... the medieval approach still tended to focus more on what is common to all human beings, rather than on the uniqueness of the individual person, the 'I'... In modern philosophy, with Descartes, the focus of attention shifts dramatically toward the subject and the subjective side of being, as seen and experienced from within, not just as an object in front of us to be captured by abstract universal concepts. In fact, the whole history of philosophy, including metaphysics, in the West can be seen as the slow emergence of the subject over the object as the center of focus and intelligibility...This modern highlighting of the subject, the autonomous, self-conscious 'I', has resulted in rich phenomenological descriptions in contemporary philosophy of the inner life of the person as experienced and lived from within, which the medievals left undeveloped or took for granted... But the balance has swung too far toward the subjective as opposed to the objective to allow a properly balanced comprehensive metaphysical vision of reality as an intelligible whole... The subjective and objective dimensions of being should come together in a harmonious balanced whole in the human person, a being with an inside (not fully objectifiable in universal concepts) and an outside (more amenable to such analysis)."
Father Clarke is far more learned than I am, and it is a bold move to say that someone of Father Clarke's erudition has missed the boat on something as fundamental as the relationship between the subjective and the objective, but I do say it. My objections are based on my reading of Plato, Aristotle and, especially, Kierkegaard.
The relationship between the subjective and the objective is not really that of two sides to being but of two approaches to being. An objective approach "cancels out" the subject in his thought; it is thought abstracted from existence. A subjective approach refuses to cancel out the subject in his thought; it is the thought of a man who refuses to forget that his thought is a fact in his life; it is thought that happens at a particular time and place and by a particular man, namely himself.
If this sounds confusing, a simple (and admittedly silly) example will help to clarify it. You are at work on the fourth floor of an office building. You smell smoke, get up up to check it out, see that the building is on fire and has been for a while. You pull the fire alarm but it doesn't work. Bursting into your co-worker's office next to your's, you breathlessly tell him the building is on fire but the alarms aren't working. You expect your co-worker to stand up and leave the building, but instead he leans back in his chair, apparently pondering something.
"Is, in fact, the building on fire?", he says. "How can I know? Maybe you are just joking with me. I do smell smoke, yes, but it is suspicious that the alarm has not sounded. This is an interesting problem. How can a man, sitting at his desk like me, determine whether the building is actually on fire?" He continues to ponder with apparently no intention of exiting the building.
"It doesn't matter if you are sure or not," you say, "you've got to get up and leave."
"Ah, yes, leaving; that may be the best course for a man in this position. But not, perhaps, the only course. What other options might he have and how will he know them?" Your co-worker continues his pondering with still no thought that he should leave the building. You give up and leave yourself.
What has happened is that your co-worker has taken a purely "objective" approach to the question of the state of the building (or the being of the building.) He has "cancelled out" his own particular existence as relevant to the question. He has forgotten that his thought is the thought of himself, a man in a particular building that may be on fire, and that such a fire will have dramatic consequences for him. You have tried to get him to take a "subjective" approach to the question of the being of himself and the building. You want him to recognize that the most significant fact is that he himself is the man in a building that may be burning.
Now the point of the example is not that people tend to forget how to respond to a building on fire. It is to give an exaggerated case, for the sake of clarity, of what it means to take an objective rather than a subjective approach to being; or, what it means to lack subjectivity in thought. Notice that in the case of your own thinking (you being the one who leaves the building) your own subjectivity does not appear as a distinct element in your thought. The difference between your thinking and your co-worker's is not anything specific we can point to. We can't point to anything in what you said and say "There is subjectivity!" No, the subjective aspect of your thought is manifested by what you did, the fact that you got up and left the building. This shows that you understood yourself subjectively; you understood that you are the man in the possibly burning building. No matter what your co-worker says, it is what he does that shows that his thought lacks subjectivity. Until he actually gets up and leaves the building, his thought lacks subjectivity no matter what its content.
The "subjective side of being" is... subjective. An objective account of subjectivity does not communicate subjectivity but rather objectivity; subjectivity cannot be directly communicated at all but can only be hinted at through indirect communication. The modern "turn to the subject" was not the discovery of the subject but the discovery of an objective analysis of the subject, which is quite a different thing. Father Clarke is right that the ancients did not have this objective science of the subjective; but they also understood themselves subjectively (the only true way to know the subjective), something we moderns often fail to do. The Original Sin of modern philosophy is in thinking that Descartes replaced the ancient understanding of subjectivity with the objective analysis of subjectivity, and that this replacement was an improvement in philosophy. In fact it was the loss of a genuine understanding of subjectivity.
Father Clarke is simply wrong that the ancient philosophers "tended to look on the world from an impersonal, objective viewpoint, as a kind of spectacle spread out before them, outside of them, so to speak..." No, this is really a description of the modern philosopher. It is the modern philosopher who looks on everything as a spectacle, including even his own personal existence. He thinks "real thought" only happens when he is disinterested, abstract, and aloof; when he is "objective." We might parody the modern philosopher by saying that he is distinguished by being the philosopher whose thought has to do with everything but himself. The ancient philosopher philosophized in the context of life, of true subjectivity. This is most dramatically realized in the case of Socrates, for whom philosophy was life, and eventually the end of life. But it holds true for other ancient philosophers like Aristotle even if it is not manifested so dramatically.
What is really missing in modern philosophy is not the objective but the subjective. The ancients did not have an "objective science of being" in the modern sense; that is, an objective science of being that involves the philosopher forgetting that he is the subject of thought. They had a universal philosophy of being that was subjectively taken, and in the subjective approach to philosophy they took account of the "I" in the only genuine manner possible.