"The human body is the best picture of the human soul." Wittgenstein, Philosophical Investigations pt.II, iv, section 25.
I use this quote because it is what began the thought processes which led to the conclusions here, not as evidence for them.
My thesis here is that the physical ought to represent, picture, or better yet embody the spiritual (by which I will mean in this post anything one would refer to as mental, spiritual, relating to the soul, emotions, cognition, etc.).
As a Christian, the most obvious evidence in favor of this is in reference to those places where the spiritual is embodied in the context of Christianity. These are, first, the human person, but that is the case we wish to understand by reference to the others; second, Christ, who is God incarnate; third, the Christian sacraments and what went before them.
In the case of Jesus Christ, God became human and thereby took on "sinful flesh" in order to bear our sins, and our sin nature in the flesh, which nature is often referred to as our flesh. He suffered, bled, and died as sinner--in our stead, or as ourselves. He represented all humans and so became human.
I think the sacraments are more obvious, and to those I now turn. In baptism, one exhibits outwardly that one has been cleansed, that one has been buried and raised with Christ. In taking communion, we take Christ in bodily and in so doing show our taking him in spiritually. I take neither of these as salvific, but both as means of grace in which we meet God spiritually in the physical representation. I count neither of these as mere ceremonies or as merely representations, but as also involving the presence of God with us in spirit in a special way. If these were merely physical representations, then they would be of no help in understanding the relationship between the physical and the spiritual in this way.
So much for the particularly Christian points, on to more broadly theistic.
I take it that all of creation pictures God, whether by choice or not and whether in the short term or long. I further take it that, in a perfect (i.e., pre-fall or once Christ returns) world, we would be able to learn directly from creation how things stand regarding the nature of God. Those who take disaster as a sign of the displeasure of God should not be wrong, and likewise those who take riches as a sign of God's pleasure--their being wrong about these things is a consequence of the fall, and so to be lamented as it is in the psalms and by the prophets. Thus I take it that the right structure of the world as a whole was meant to be one of imaging the spiritual in the physical. It may be possible for this to be the case and yet particular physical things not be intended to relate in that way to particular spiritual realities, but I doubt that it is likely that that is how it is supposed to be. That is, I suspect that particular physical realities correspond relatively straightforwardly to spiritual realities as regards what they are supposed to image. Thus, human body is to picture human soul.
On to broadly philosophical points.
Insofar as what I am referring to here as the human soul is what directs the human body, it seems natural that it would exhibit itself in the human body, and insofar as there is design, it seems designed to do so. Thus there would seem to be a malfunction if the human soul was not pictured by the human body.
If the normative in no way shows up in the physical, then we cannot charge anyone with guilt on account of actions performed, but only on account of intent divorced of physical content, e.g., intent to commit murder, but not intent to drive an axe through the skull of a self-moving human body's skull. If the normative does show up in the physical, then I would expect it to do so by means of, at least, what is harmful or beneficial to human well-being, broadly construed. Such things would then indicate what is good or bad to us.
What is conducive to our well-being, broadly construed, is what is conducive to our being what we are as fully as possible. We are humans which are both spiritual and physical, with the spiritual directing the physical, by and large. Thus, what is good for us is, in part, what is conducive to our exhibiting who we are as spiritual persons in what we are as physical bodies.
There is much complication which may follow, such as balancing changing insides versus changing outsides, but the point here is to establish that, all else being equal, one's spiritual person should show up in one's physical body. I take it, further, that this extends to speech and to social life and exhibiting spiritual relations via physical ones, which we do naturally, indeed, instinctively, by adjusting distances between us, shifting foot positions, crossing arms, etc.