I am my body.
I am not just my body.
My crankiness due to lack of sleep, for instance: it is still my crankiness, even though I can point to its biological causes. My crankiness is in my body, so to speak, but it is still a feature of my person that I am cranky.
It is possible to say to oneself, "I did not get enough sleep, I must beware of my crankiness." Consider: "be angry, but do not sin." I may, in my person, experience human emotions, yet I may act contrary to them (emotions are not the only motivators).
This is to subordinate the emotions to the "I" who chooses. The emotions are still to be considered a part of me, but not the whole. This is the subordination of the part of a person to the whole of the person.
The emotions are, therefore, linked to the biological. Nevertheless, even when we know the biological causes of our emotions, we do not necessarily disregard our emotions. That is to say, even when we consider the emotions fully explained by biology, we do not on that account disregard or silence them. Though we may disregard our emotions when we regard the causes as not warranting them.
All this goes to show that the mere fact that something has biological causes does not simply on that account absolve the subject of responsibility for them, nor does it entail that those things are not part of the person.
A human person interacts with other human persons and with the environment only through their bodies. My body is how I interact with what is not me.
Could a person, or part of a person, exist apart from being expressed?
Is there anything more to a person than the expression of personhood?
Surely, my motives are not fully expressed, yet they are fully a part of my person. Is a person truly without anger simply because the anger is not expressed? But anger has a physical component to it, and even apart from that we know that anger can be said to fester and build. The anger exists, that is to say: it will show itself. This answers the first question in the negative.
To the second I would like to say that there is more to a person than their expression, that there is something it is like to be conscious, to be a person, which I know (only) firsthand. But let us refine the question some more.
Can there be an expression which appears as the expression of a person, without there being a person?
We would not know. At the very least, we could not hold that such an illusion occurred both regularly and naturally, lest we lose confidence in the personhood of other humans. If such an illusion could be expected, then it would no longer be an illusion--we would not read those things as an expression of personhood.
What I am puzzling over here is the mind-body problem: how is the conscious subject related to his physical body? This is different from, though related to and frequently identified with, the question as to whether we have non-physical souls or not. Many, if not most, answers to the mind-body problem identify the mind with the soul, but that is to beg other questions which I do not intend to address here just yet (viz., what is the mind? What is the soul? How are they related?). What I have expressed above are reasons for being suspicious of mind-body dualism. They do not invalidate soul-body dualism, so long as the soul and the mind are not identified with one another. It is possible for soul-body dualism to be true and the mind to have aspects which cannot be accounted for without reference to each, yet the mind not be a third thing (for that reason, I will need to address the questions in the above parenthesis eventually).