The question of a wife's submission to her husband is a complex one, but perhaps it comes down to this: what does experience with reality tell you?
This is the rub, because our experience is not infallible; there are deeper mysteries and reality is more complex than we can grasp as individuals, and if we place too much emphasis on our own understanding (and very intelligent people tend to do this more readily), we can miss the deeper truth. For example, Aristotle's methodology, though a great step forward in human thought, was not infallible. He worked from the observable, physical world to the metaphysical, and attempted to show the fundamental order of the cosmos born of the synthesis between biological nature and metaphysical nature; later Aquinas followed this lead in his own great synthesis of Christian doctrine flowering from the Jewish Torah and, in part, their thought, and Aristotle and Plato. It is essential to discover how Aquinas derived his own methodology leading to political principles, because in a true medieval sense, Aquinas sees the cosmos as a harmonized whole, from the physical to the highest levels of metaphysical truth. His synthesis is deeper than just between the ancient Greeks and Christian thought, but an attempt to align Jewish and Greek thought, both streams a hermeneutic lens to understanding the New Testament and the Tradition of the Church. So, we first start with the Greeks, specifically Aristotle, whom Thomas simply calls "The Philosopher"; I always "hear" him inflecting "the," "the Philosopher," indicating that Aristotle is the primary Greek, pre-Christian epistemology and methodology upon which he will rely.
This methodology starts long before Aristotle, however: I believe it to be the essence of "the Greek miracle": the Ionian Pre-Socratics are generally characterized by a major shift in epistemology, from relying solely on mythology, a dependence on what was handed down or given to humans by the gods, to a search for foundational, constant, discoverable laws of nature. In other words, they somehow took the Promethean fire of knowledge into their own hands, a growing belief that they lived in a cosmos, a universe ordered by fundamental laws of nature, not a battleground of whimsical personalities one step away from chaos. Thales of Miletus, for example, says, "Everything is full of gods"; at face value, this may seem like an affirmation of the more primitive, Hesiodic and Homeric worldview, but it is most often interpreted as meaning that all things, from the observable to the metaphysical, have a certain ordering towards purpose or end, from a rock to the gods; this interpretation is upheld in the words of Thales' student Anaximander: "The origin of all things is the apeiron (the boundless or the infinite), and it is from this that all things arise and return." The apeiron becomes both an origin and end, creating a law that is not based on a changeable, Zeus-like character who distributes law based often on personal desire or persuasion leading to the supplicant cults.
Aristotle is a descendant of this Pre-Socratic and Socratic insight; his hylomorphic system is based on the dual foundation that everything in existence is made for a purpose and that this purpose, or telos, is observable first in the physical world, all knowledge beginning first in apprehension through the senses, and then concomitantly observable in the rational, the metaphysical, through conceptualization and universalization of natures (substantial forms). Mathematics, of course, is one, if not the, major jumping point from physical to metaphysical, which is one reason, perhaps, mathematics engendered ratio-religious cults. Aristotle, based on observation of the natural world and the search for the fundamental laws of nature, created his great works, The Physics and the compilation we label The Metaphysics.
The foundational nature of this shift from mythological imposition of "order" to rational, scientific discovery of law cannot really be overstated, and Aquinas saw the truth in it, perhaps seeing a way to prove through observation and argument the Creator's order: eternal law, divine law, natural law in a great symphony, with which human behavior and law, to be considered truly just and teleological, producing salvation and happiness, must harmonize. Interpretation of Aquinas' thought on any subject, therefore, has to take Aristotle's method and conclusions into account, and it seems apparent that Aquinas' method relies at least partly upon the extrapolation from the physical to the metaphysical, synthesizing this with that handed down from Jewish and Christian thought.
In the Summa, on the question of a woman's nature, however, I believe Aquinas follows Aristotle into some error based on faulty observation of biology. In the First Part, Question 92, Article 1, Aquinas indicates that the woman is made as a helper for man in terms of generation, as a passive vessel to his active seed. This was built on the Aristotelian idea of the passive and active principle present also at the fundamental level of logic (prime matter activated by form). However, the biology upon which this is all based is simply wrong: a woman also has a "seed" and an active part in generation just as a man does; in the sexual act, the man does play a more active role, but not in actual conception, and we don't fully understand the possibility that woman's state of mind and her body can, at times, also affect conception, even more subtly than and beyond the variations in fertile times of the month. Therefore, early observations in biology which helped build an entire physical, political, and metaphysical structure of thought about women were not infallible, and so there may be other areas which are also faulty.
Furthermore, women are in some ways more than just active, equal partners in the physical generation of the human race; indeed, her part is greater: a woman is born with her eggs, and so a mother who has a girl in her womb is responsible not just for the continuation of one of her own eggs, but also an entire new potential generation of human beings...this is a form of stability and foundation for "like to like" (in Aquinas' words) that the male semen does not have: his seed is being generated and dies in cyclical flux with variations on a theme in terms of DNA. Moreover, the child does not fully "leave" the mother, as shown by fetal microchimerism, the process by which part of her child's DNA stays with her for decades, perhaps even for the rest of her life. Women therefore do not just provide a vessel for future human beings, they are an active and continuing foundation for them. In a slightly ironic twist, creating a dynamic hierarchy, a man could be in some sense considered a woman's helpmate as she bears this great task for the good of others, for the good of society and the common good of earth and heaven. In terms of a woman playing an active role in both realms, Mary Theotokos is the highest example of this, and her fiat is a sign of an active part in the generation of Christ. Was she an equal part? Vis à vis the Holy Spirit, of course she was not—not equal in nature. However, I venture to say that in His Divine humility, the Holy Spirit asked her permission, which is an indication of His granting her equality in this decision; her seed was definitely needed, and it is fascinating to think that Christ's human DNA came only from her. This is why spiritual, emotional, political, or even physical (as in rape) domination is so egregious: it is a sign of one who treats the woman as a passive unequal, and this is a powerful instance of the difference between the pagan gods and the True God: the rape and seduction of women and goddesses in the mythologies, the temple prostitution, etc, is in stark contrast to how God interacts with Mary. God would have known that this would speak volumes to the pagan world: a woman is certainly to be treated as an equal by men, if even God asks permission of a woman to impregnate her.
What was derived from the faulty understanding of generation? Aquinas in the section mentioned above seems to indicate that the male is the template human, which would make sense if the male carried the only genetic seed for offspring; the woman would be simply a vessel for the seed to carry on, and because the male seed in the case of a female child would not be a "true image" of the male, originally human seed, she is, in effect, a defective male. This sets into motion a principle upon which many other conclusions have been drawn.
One is the idea that women are simply not rational to the same level as men; also from Aristotle, the idea that women are not capable of the highest activity of human life, the political life, may have been born from two physical sources: the generative, active principle in conception echoing the active formative cause versus the passive, less intelligible matter, and the cyclical, changing body of the woman through menstruation. Men were considered consistent in their physical life; women were considered unstable, weaker physically, and prone to emotional fluctuations. This has some truth to it, but hormonal changes are not necessarily indicators of rational qualities or absolute capability for participation in political society as leaders in certain areas. Besides, beyond childrearing years, women become emotionally similar to men in many cases, as the hormonal fluctuations recede—and many women do not fluctuate emotionally to any noticeable degree; the more serious emotional fluctuations are often a result of hormonal imbalances, just as many men are overly-prone to the instability of aggression due to, perhaps, a hormonal imbalance.
Also, Aristotle lived during a period in which women were oppressed: kept from education and opportunity to develop their rational faculties, their lives and especially their intellects were often atrophied and even discouraged; as late as nineteenth-century England, Jane Austen makes the quip, in one of her letters, about the "unfortunate quality of intelligence" possessed by any woman hoping for a good marriage. Aquinas, though, should have been more aware: as Regine Pernoud shows masterfully in Women in the Days of the Cathedrals, women in the early medieval period, for hundreds of years across Europe, held positions of leadership: landowners, abbesses for both men and women, judges, educators, etc.. Hildegard Von Bingen, who lived at the height of this Christian development and freedom for women, is one such example: she was a polymath, a genius in a number of fields, which belies the idea that women cannot, by nature, rise to great rational heights. It was only with the return of the Roman law in the thirteenth and fourteenth centuries that women began to lose their places in political life; Pernoud relates this with some sadness, because she acknowledges, as is obvious to anyone, that masculine gifts and feminine gifts for society are not the same, and with the feminine relegated to silence and obscurity, much was lost. Therefore, like Aristotle who lived in a culture that did not give women opportunity to develop properly as fully rational human beings, Aquinas may also have had a faulty experience of the capability of a woman; perhaps like the Greeks and Romans before him, he had a certain prejudice, leading him to declare the feminine, according to physical, bodily nature, defective in comparison to a man.
Again, one should, albeit cautiously, look at direct experience. Anyone who has taught at the college level, once men have caught up in terms of development, can see clearly that the young woman sitting in a class is as fully rational as the young man sitting next to her.
Of course, Aquinas makes it clear that according to the spiritual, by grace, women are equal to men. However, this seems to raise an issue: if the body is the form of the soul, and a woman's body is a defective male body, then why not her soul? Aquinas seems to indicate "by grace" and so, like Luther's doctrine of grace covering sin, perhaps Aquinas is indicating that God's grace covers the defective human soul of the female. It is as if women are, by nature, retarded. However, does God make something defined by the defection from another thing?
This is where I feel that John Paul II's Theology of the Body becomes, perhaps, a true development of the issues in Aquinas' and even Augustine's thinking on this question. Like Aristotle and Aquinas, John Paul II creates a synthesis, a leveled, ordered system of thought based on, or including the physical, in the sense that the physical is semiotically related to the metaphysical: the physical is a sign of greater realities, as it seemed to be for both Aristotle and Aquinas. However, John Paul II also sees analogically, namely that the human in spiritual, rational, and physical nature is also created imago Dei, to be an image of God, and that the complementarity of masculine and feminine into a unity is a sign what it means to transcend individuality in an out-flowing of love; therefore John Paul II sees not a hierarchy of inequality, defectiveness, and passivity versus activity, but rather self-gift, both sexes imaging this essential characteristic of God. The physical bodies of a man and a woman are made for unity, for a movement out of original solitude and into community, both through the conjugal act and through conception of a new person, the beginnings of a society. Physically alone, the male sexual member calls for another; it is incomplete; by itself it makes no sense, just as the female reproductive structure calls for another. This deeper, more biologically-correct understanding of male and female bodies can correct and deepen our understanding of the roles that men and woman are potentially called to in society, both the society of the family and the larger society. The sexes need each other, and are not fully complete without the other: thus the principle of complementarity rather than political hierarchy.
Complementarity indicates fundamental equality: without the other puzzle piece, the entire puzzle is incomplete: isn't this what Adam indicates in the Garden, and why God gave him one who could be his helpmate, his friend, his other half? Would Adam have been satisfied with a less rational being, a defective male? Would God have made a being at the crown of creation as defective, reaching back down towards the animal, the irrational? This does not follow the pattern of Genesis, which moves from the nonliving, to the living, to the animate, to the sentient, to the rational. To end with something defective seems to contradict the arc of Genesis, and patterns like this in the Torah are paramount: no detail is unimportant.
The next question I always get is this: What about St. Paul? This actually, and rightly, brings up the other epistemological method that Aquinas was synthesizing with the Aristotelian: the Judeo-Christian. St. Paul, steeped in the Judaism of his time as a Pharisee, would have thought like a Jew and therefore taught like a Jew of first-century Palestine. Just a caveat: I am not arguing for the historical-critical method of reading the New Testament, denigrating the role that the Holy Spirit played in producing the New Testament; I am simply saying that St. Paul would most likely have been using the epistemological method he knew from Jewish tradition to teach, one which is almost the polar opposite of Aristotle, though not contrary to it in the end. In fact, Aquinas is one Christian thinker who sees these two epistemological methods as complementary; this makes Aquinas' synthesis all the more admirable, though I am arguing that these two methodologies being different can create confusion about the nature of a woman in the teaching of St. Paul.
What is a synthesis, a point of agreement, between Aristotelian thought and Jewish thought (at the time of St. Paul)? The most basic is that there is a cosmos, a work of art that, in both the whole and parts, is teleological. It is not just that individual parts have purpose, from the tiniest quark to the greatest angel, but that they are all created to be in harmony with a Prime Mover, or, for the Jews, the transcendent Creator, who is a Person. This is what allowed Aquinas to synthesize the two traditions of epistemology. However, in order to more deeply understand the nature and role of a woman, we have to know which tradition we're interpreting. What is the major difference?
The starting point. For the Jews, this was not observation of the physical world or the use of human rational laws as exemplified in the mathematical language of beauty and order to derive metaphysical laws, working backwards toward a Prime Mover; for them, all deep, true understanding began with the Torah, or, more specifically, God speaking to them directly through both word and action: it was the imitation of God; it was beginning with the revelation of God, the ultimate understanding of His law given to them in the experience of God's power, His care, His presence, and finally the codification of this relationship in the Ten Commandments from which all other laws were derived. The Jews therefore were unique: they were the bride of God, His children, and He taught them truth directly, from which they derived their religious, social, and political structures. How did this derivation happen? There are a number of means, but comparison, specifically analogy, were common and powerful tools. We see Jesus using this in the parables, one of his most important teaching tools; these generally fall under the "Midrash," the creation of new teachings based both in the familiar world and in subtle teachings of the Torah, connecting them to teach deep theological truths to a limited human mind. And Jesus also structures His Gospel on the Torah: He states that he came "to fulfill the Law, not to abolish it" and to deepen understanding of the Law through statements in the Beatitudes starting with "you have heard it said...but I say...": each time not contradicting the law but rather showing the original, deepest meaning of the Law in line with whom God is. Another method, "Binyan Av," creates analogous application of the Torah to new teaching about human life. In other words, a case can be made that St. Paul, starting with not the Torah, but with Christ's Gospel, was yet using the same analogical methods: creating new teaching about marriage by analogy to Christ and the Church, simultaneously explaining more fully the nature of Christ's Body through marriage as a familiar sign, and asking couples in turn to be witnesses, or signs, of this reality: to be a testimony of the Deeper Reality of Christ and the Church to the outside world.
How, then, do we read St. Paul about the submission of a wife to her husband? One can read this a couple of ways, but it depends, I think, on how one comes to the reading: if based on the assumption that women are defective men as Aquinas seems to teach, then the submission becomes a political necessity, the wiser (more rational) ruling over the less wise (making women just a little more wise than the children in the house). If all this were true, then it would be self-evident that a man rule absolutely over his household; it would make him a "little god." However, conversely, if one comes to the reading with the lens of complementarity and self-gift of two equals—equal by nature rationally and spiritually—then suddenly, the submission becomes a spiritual sign for something much greater: the Church as Bride, Christ as Bridegroom. Christ is, by nature, greater than His Bride, but this is because He is God. This is why I believe St. Paul says, "...but I am speaking here of the Church...." The Christian marriage between individuals becomes a sign of the submission and humility present in the Trinity, and the submission and humility of the Bride of Christ—and yet she is also His Body, one whom He loves and cares for as His own. When one studies the analogy, synthesizing the Bride and also the Body, one can ask: is the head, a part of the body, greater than the whole body? This is the great and surprising thing that St. Paul teaches about the nature of Church: Christ really does raise Her to be be one with Him; He sees Her as a continuation of Himself in the world, and perhaps St. Paul, following Christ's astounding teaching on marriage, "they are one flesh," is using this idea to show just how much Christ loves us: "May they be one with Me." However, in terms of individual marriages between people, an analogy has limits, because this is, of course, different from an individual wife and husband: many a sinful husband has had a saint as a wife, one who has interceded for him, in a sense, helping to save and in marriage, challenging him to cleanse his soul; of course, the reverse is also true. This is just one example demonstrating that the analogy of the Bride and an individual bride, like all analogies, has its limits and the higher object of the sign cannot be imposed completely on the sign itself, because the sign is, in a sense, too small; the sign can only point to the higher reality in a partial way (or the sign and the higher reality would, in effect, be the same thing).
Therefore, what is this submission in a marriage? Within and beyond individual equality, it is a sign, a Christian witness of the nature of the Church and the love Christ has for her, as His Body. The husband is to be a sign of Christ, who gave His own life for the Church, who serves her in deep humility, a servant leader; the wife is the Body in receptivity and response: not Aristotle's passivity, but Mary's fiat. However, this is not something determined by physical and rational natures, but analogical to it, which makes the "self-gift" out of what St. John Paul II calls "original solitude," all the more beautiful because it is a choice; choice, free-will, upon which the existence of love depends, is a resounding modus operandi of God, even with His own Son. God makes human nature complementary, needing an other, made to be complete in another. This is not a defect, but a sign of love and fecundity through that love: it is the desiring of the good, of our completeness in another, creating the majesty and beauty of creation, and it is, in a sense, analogous to the ever-flowing self-gift of the Trinity, a mutual complementarity and submission of equals.
Does it mean that roles are absolutely fluid and that there is no real difference between men and women? No. Using the Jewish analogical method, the great Orthodox theologian Paul Evdokimov writes in Woman and the Salvation of the World that the role of a man is that of a John the Baptist, or, I would add, a St. Joseph: he who, through kenosis, is fathering through emptying of the self for the good of another; Evidokimov says that the role of a woman is Mary Theotokos, the reception of God; on the human level, a deep and personal reception of the other. A man also, as a priest, has a specific role of alter Christus, another Christ. This, to me, indicates a certain spiritual role, a headship; I believe all men carry within them this deep, Christlike kenosis, which indicates servant leadership (think of Christ washing feet). However, all Christians, following the assertion " in Christ there is no male or female," are equally called and equally capable of becoming Christlike. What about the particular roles of men in the family and in society? Speaking from biological observation, the Greek method, men tend to compartmentalize more easily (interestingly, perhaps a result of a chemical "wash" partially separating the hemispheres of the brain at about six weeks of life) and can therefore set their feelings and a complex, holistic picture aside in order to see the fundamental choices at stake. In this, they may offer a situation the ability to empty the self and simply serve the highest good: we see this in defense of family and country. Women, on the other hand, are generally more consistently personal and can take into account even tiny details; thus, they do not as often fall into reductionism: all these ideas are, of course, generalities. However, they may point to certain roles in a situation pertaining to those differences. In the end, though, even these differences are not in a strict hierarchy, but rather are dynamic roles, depending on the circumstances, and I believe, work most effectively in a relationship of complementarity.
With the principle of complementarity, many beautiful areas to explore are opened: as St. Edith Stein wrote, society needs both the genius of the feminine and the genius of the masculine in all areas; the feminine tends to see slightly differently, hers a nurturing, personalist sight; the masculine a powerful categorical sight and an awareness of danger. These are, of course, massive generalizations, but like Edith Stein, I believe that we need women lawyers and doctors and politicians as well as mothers, and we need male counterparts in all areas to fully serve the common good, as well as fathers.