Saint Teresa of Avila has an important discussion of the soul and self-knowledge in her work, The Interior Castle (which can be found on-line here), a spiritual classic written in 1577 or shortly before. There she pictures the soul as a castle made of diamond or crystal, in which there are many rooms (aposentos), "just as in Heaven there are many mansions" (moradas) (1.1.1). The 'rooms' of this castle are connected with self-knowledge, for Teresa immediately goes on to say:
It is no small pity, and should cause us no little shame, that, through our own fault, we do not understand ourselves, or know who we are. Would it not be a sign of great ignorance, my daughters, if a person were asked who he was, and could not say, and had no idea who his father or his mother was, or from what country he came? Though that is great stupidity, our own is incomparably greater if we make no attempt to discover what we are, and only know that we are living in these bodies, and have a vague idea, because we have heard it and because our Faith tells us so, that we possess souls. As to what good qualities there may be in our souls, or Who dwells within them, or how precious they are -- those are things which we seldom consider and so we trouble little about carefully preserving the soul's beauty. All our interest is centered in the rough setting of the diamond, and in the outer wall of the castle -- that is to say, in these bodies of ours. (1.1.2)
So the idea is this: The soul is the castle itself; but the soul also in a sense occupies different rooms of itself through its knowledge of itself. As she notes, linking the issue of self-knowledge with prayer,
But you must understand that there are many ways of "being" in a place. Many souls remain in the outer court of the castle, which is the place occupied by the guards; they are not interested in entering it, and have no idea what there is in that wonderful place, or who dwells in it, or even how many rooms it has. You will have read certain books on prayer which advise the soul to enter within itself: and that is exactly what this means. (1.1.5)
Most of our self-knowledge is purely superficial - the outer wall of the castle, i.e., our body. Teresa is very insistent that there are many, many, many rooms in the castle; but the rooms also fall into rough groupings that can be distinguished according to interiority. The innermost room of the castle is the room "where the most secret things pass between God and the soul" (1.1.3). The Interior Castle is a guide to moving, through prayer, from the sort of self-knowledge we have in the outer part of the castle, to the sort we have in the inner part of the castle. (She divides the groupings into seven; of these we cannot get much farther than the second on our own - beyond that we need humility, prayer, and considerable reflection and meditation.) One of the interesting aspects of this whole picture is that Teresa was not the last to make use of it. Edith Stein uses it in Finite and Eternal Being. Edith Stein (1891-1942), for those who don't know, was a student of the philosopher Husserl. Jewish by background, she eventually converted to Catholicism and entered the Benedictine Order as a Carmelite. In 1942 the Nazis arrested her and sent her to Auschwitz-Birkenau, where she died. She was canonized in 1998, and so is known variously as "Saint Edith Stein" or "Saint Teresa Benedicta a Cruce," which was the name she took in honor of Teresa of Avila. The interior castle is introduced in part VII, section 3. There she notes (quotations are from Finite and Eternal Being, Kurt Reinhardt, tr., ICS Publications, Washington D. C., 2002):
The soul as the interior castle--as it was pictured by our holy mother Teresa--is not point-like as is the pure ego, but "spatial." It is a space, a "castle" with many mansions in which the I is able to move freely, now going outward beyond itself, now withdrawing into its own inwardness. And this space is not "empty," even though it can and must receive and harbor a fullness in order to become capable of unfolding its own individual life. (p. 373)
The soul 'dwells' in various aspects of itself: in the body, as sentient; in the spirit, as extending outside itself to recognize a world of persons, events, and things; and in "the personal I" or "pure ego". Stein is careful to indicate the point at which she is going beyond Teresa, saying, "St. Teresa was not interested in the question of whether the structure of the soul, aside from being the abode of God, has an independent meaning of its own and whether there is perhaps another entrance 'portal' to the soul's inwardness besides contemplative prayer" (p. 598 n. 33). In Stein's understanding of the interior castle, the dwelling-places are a significant fact about the very nature of the soul's 'inwardness' or self-consciousness; and the other entranceway is what she calls the "awake and conscious ego-life" (p. 375). It plays an important role in her attempt to clarify what it is to be a person. We have a genuine sort of soul-structure, a multifacetedness, in our self-knowledge; spatial metaphors are an attempt to characterize this, given that we don't have more convenient words for what is being discussed. She agrees with Teresa that the "ego which apprehends, observes, and works upon its own self as if this self were a purely external thing evidently does not have its seat in the interior of the castle" (p. 433), and that self-knowledge is closely related to interiority. As she says:
In its innermost being the essence of the soul is completely overt to itself. When the ego lives in this interiority, i.e., in the ground of its being where it is truly at home and in its own, it experiences in some measure the meaning of its being and feels the collected power that precedes the division into individual powers or faculties. And when the ego's life issues from this interiority, it lives a full life and attains to the height of its being. (p. 438)
This transformation to interiority is a gradual process; in particular, it is a gradual process in which the person becomes more fully what they are called to be: the call to interiority is an appeal to the person, to the intellect, to the free will. And we do experience a call to interiority. It does not compel, but to dwell in our castle in a more interior way is to understand ourselves more fully and to be more at home with who we are; the call to interiority is the call to 'take a stand' with respect to what sort of persons we will be, the voice of conscience: "Reason and faith are both appeals of the soul, calling it 'to enter into its own self' and to mold human life from the innermost center" (p. 440).
This only barely scratches the surface of the investigations of the two Teresas on this point. I find it immensely interesting from a philosophical perspective; in part, because I think they are both on to something very important about the nature of self-knowledge, and in part because it highlights that there is an immense amount of moral psychology and philosophical anthropology locked in spiritual classics. It's perhaps worth noting, too, that recognition of this is important to doing more justice to the actual participation of women in the Colloquium of Ages that is the history of philosophy. There are many important philosophical insights from women located in works of piety and spirituality with which, for various reasons, they often were in more of a position to write than they were to write any treatise that would be more stereotypically 'philosophical'.