As today is the Feast of the Guardian Angels, and St. Thomas Aquinas is called the “Angelic Doctor” partly because of his teaching on the angels, the reader will excuse a dense neo-scholastic reflection on the Gospel of the Feast.

See that you do not despise one of these little ones; for I tell you that in heaven their angels always behold the face of my Father who is in heaven. (Matthew 18:10)
The greatest good realized in creation, that which the Creator primarily intends in creating, is the good of the tranquility of order, the beautiful harmony that unites all creatures. This is the primary intrinsic good of creation, and the most perfect image of the God Himself, the separate and transcendent good of all things. The goodness of each individual consists in in own participation in being, its own reflection of an “aspect” of the divine Glory, but consists even more in the contribution that it thereby makes to the order of the whole.
Now the order of the whole of creation consists in two things: distinction and governance. In the distinction between different kinds of being and different levels of perfection, and in the governance of lower things by higher—the ordering of the less noble by the participated providence and power of the more noble. By governance the higher creatures help the lower contribute to the harmony of the whole, and finally “return” to the separate good of all things.
The is a great difference in the degree of participation in cosmic order between irrational creatures on the one hand, and rational and intellectual creatures on the other. Irrational creatures, since they lack true interiority cannot attain to the order of whole by knowledge or love, thus their participation in ballet of creation is extrinsic, imperfect—that is, the good of the universal order is a good to which they contribute in a small way, but it is not good for them, they cannot appreciate it. There participation is strictly speaking good for rational creatures, since only rational creatures can understand and enjoy their participation. The principle parts of the universe, the things of which the universe primarily consists, are thus the rational and intelligent creatures. They are the creatures that the universal good is for, in the sense that they enjoy it (Though in a more proper sense they are for it, as the universal good is more good than any particular good).
Since universe consists primarily of intelligent creatures, in the sense that they are its principle parts, and since intelligence is found most properly in purely spiritual creatures, St. Thomas argues that it is fitting that the “intelligences” (angels) exceed all corporeal creatures not only in the intensity of their being but also in their variety and number. As Lawrence Dewan puts it:
Thomas thinks there are good reasons [even apart from Revelation] to propose [the] existence [of angels], and their existence in number and variety such as to surpass incomparably any number of corporeal beings. The created universe, as St. Thomas conceives it, is overwhelmingly spiritual as to its ontological status, an assembly of spiritual substances or persons. ‘The universe’ is primarily a group of persons.” (Wisdom, Law, and Virtue: Esays in Thomistic Ethics, New York: Fordham University Press, 2008, p. 273)
However wonderful the numerical superiority of spiritual things over corporeal, far more important, and better known, is their intensive superiority to corporeal creation. Charle De Koninck has a wonderful summary of this in the second part of Ego Sapientia, which is concerned with the lowliness of Our Lady in the order of nature. He writes:
At the peak of creation, seen from the purely natural point of view, one finds the angels, pure spirits, beings very perfect according to substance and operation. Their essence being simple, each one of them constitutes in himself a complete and individual species subsisting outside of every naturally common genus. Each exhausts a degree of being. Radically hierarchised, each angel occupies an absolutely determined place in this hierarchy. Even the most inferior pure spirit constitutes in himself a universe incomparably more perfect than the cosmos and humanity together.
De Koninck proves this by considering how pure spirits are naturally superior to human beings, the most perfect corporeal thing. While man is composed of matter and form, of potency and act, and thus has the principle of his own passing away with himself, the angels are entirely necessary—the do not contain in themselves any principle of non-being. This is why in the world of men, unlike in the angelic world, so much is a matter of chance:
We are living at the border of the universe in which we are diffused, both as regards substance according to quantity, and duration according to time. Our days and places are uncertain. All here below is variable and precarious, and it is only by great effort that we sometimes succeed in impressing a momentary direction upon things. It is only by a habituation that blinds us and by a kind of animal resignation that we have become unconscious of the immense confusion in which we live, where violence alone seems capable of awakening us. Our substance is truly at the border of being.
The contrast is even starker if one looks at the act which is most defining of intelligent beings: knowledge. The angelic mind is in act from the very start of its being, a ray light as it where that takes in all things, that comprehends all creation with very few and powerful ideas. But the human mind begins in darkness, a purely potential intellect, which only begins to find some sparks of light through abstraction from exgternal, corporeal things: “The need of shadows of the sensible world originates in the weakness of our intelligence. By nature our rational life is the least perfect intellectual life conceivable.” (Ego Sapientia, ch. XIX)
Nevertheless, despite all this imperfection, human life, is an intellectual life, and as such it is able to attain to the good of God’s manifestation of Himself in the order of His creation, and (through grace) beyond that to the vision of God Himself. And this is what gives us our dignity.
This dignity is manifested by the fact that each human person has their own guardian angel—a pure spirit, who sees the beatific vision of God, and who is yet concerned with governing an individual man. We are part of the corporeal world of things, that comes to be and passes away, and yet we transcend it. God’s providence is chiefly concerned with things that endure forever, and only secondarily with passing things. Thus St. Thomas teaches that the angels concerned with governing the corporeal world are not set over individual things (destined to pass away), but only with the species of things which perdure. But individual human persons are not destined to pass away, and thus each one has a guardian angel, a governing intelligence. Children manifest most clearly the human condition of potentiality, ignorance, and weakness, and yet their angels in heaven always behold the face of the Father, and the task of those angels is to lead the children themselves to that vision, and in that destiny lies their dignity.