On the Teacher

Overview

About fifty pages, Question eleven of Aquinas’s Disputed Questions on Truth, De Veritate, a large collection of questions he composed and defended in formal academic disputation during his years teaching at Paris, roughly 1256 to 1259, early in his career as a regent master. Disputed questions were a standard genre of medieval academic exercise, in which a master proposed a question, considered a range of possible objections and counter-arguments, and then worked through to a resolution that engaged seriously with the strongest opposing positions rather than simply dismissing them.

The title, and the question’s central concern, directly recalls Augustine’s own dialogue called The Teacher, De Magistro, written roughly eight centuries earlier, in which Augustine, working through a conversation with his son Adeodatus, had argued that human words and human teachers cannot, strictly speaking, cause knowledge in a learner at all; genuine understanding, Augustine concluded, comes only from an inner light, ultimately identified with Christ as the inner teacher, that illuminates the mind directly, with human speech serving merely to prompt the learner to consult this inner light rather than actually transmitting knowledge itself.

Aquinas takes up Augustine’s question directly and by name, structuring his own inquiry as an extended engagement with it, in four articles: whether one human being can properly be said to teach another, or whether only God can be said to teach in the full sense; whether a person can be called his own teacher; whether angels teach human beings; and whether teaching belongs properly to the active life or the contemplative life. The first article carries the bulk of the philosophical weight and is what most readers mean when they refer to this text as On the Teacher.

The argument

Stating Augustine’s challenge. Aquinas begins by laying out, with real fairness, the strongest version of the position he will eventually qualify rather than simply reject. Augustine’s argument, as Aquinas reconstructs it, holds that genuine knowledge consists in the mind’s grasp of truth, and truth is available to the mind only through an inner illumination that no external human agent can supply directly. A teacher’s words, on this view, can prompt a student to look within and consult this inner source of illumination, but the words themselves do not and cannot cause knowledge, any more than knocking on a door causes the person inside to open it; the knocking is merely an occasion, while the actual opening is done entirely by the person inside, acting from their own resources.

Why this cannot be the whole story. Aquinas does not simply reject Augustine’s picture; he takes it seriously enough to preserve much of its insight while arguing that it, taken alone, cannot fully explain what actually happens when someone learns something from a teacher. His route to this qualification runs through a careful analysis of what learning itself consists in.

Learning, for Aquinas, following Aristotle, is a movement of the mind from things already known toward things not yet known, a process he compares closely to natural processes of development and actualization more generally. Just as a doctor does not create health directly, the way an efficient cause like fire directly produces heat, but rather assists and cooperates with a patient’s own internal natural power to heal, applying the specific means, medicines, treatments, that this internal power then uses to bring about recovery, a teacher does not implant knowledge directly into a learner’s mind the way one might pour water into an empty vessel. Instead, a teacher presents signs, words, examples, ordered demonstrations, that the learner’s own natural reason then actively uses to move itself from what it already grasps to a new conclusion it did not previously grasp.

On this account, teaching does genuinely cause knowledge, and Aquinas is explicit in disagreeing with any reading of Augustine that would reduce teaching to mere occasion-making with no real causal contribution at all. But the causation involved is what medieval philosophy calls instrumental or mediate rather than direct: the teacher is a genuine cause of the student’s coming to know, while the proximate, immediate cause of the actual act of understanding remains the student’s own intellect, exercising its own natural capacity for reasoning, now guided and assisted by what the teacher has presented.

Why signs are necessary, and what they can and cannot do. Because a teacher cannot act directly on another person’s intellect the way one thing in nature can act directly on another physical thing, teaching necessarily proceeds indirectly, through signs external to the mind, spoken or written words, diagrams, worked examples, that the learner’s intellect must then interpret and actively use. Aquinas is attentive to the limits this imposes: a teacher can arrange these signs skillfully, in an order calculated to lead a learner efficiently from known premises to a previously unknown conclusion, functioning much as a skilled scientific demonstration does in leading reason step by step toward certainty, but the teacher cannot guarantee that any given learner’s intellect will actually complete the movement, since that completion depends on the learner’s own active engagement and natural capacity, which varies between individuals and is not under the teacher’s direct control.

God as the primary teacher, and the human teacher as genuinely secondary cause. Having established that human teaching is a real, though instrumental, cause of knowledge, Aquinas returns to and partially vindicates Augustine’s original insight. He affirms that God is indeed, in the deepest sense, the primary source of all human knowledge, since the very natural light of reason by which any human intellect is capable of moving from known truths to new ones is itself, on Aquinas’s broader metaphysical view, a created participation in divine light, sustained continuously by God as the ultimate cause of all created causal power whatsoever. In this sense, Augustine is correct that God alone is, finally, the primary and universal teacher of all human beings.

But Aquinas insists this does not eliminate the genuine, secondary causal role of the human teacher, any more than God’s role as the ultimate sustaining cause of all natural processes eliminates the genuine causal role of, for instance, a doctor curing a patient, or a farmer cultivating a crop. Secondary causes, operating within and dependent upon the primary causal power of God, remain real causes of their proper effects, and a human teacher’s presentation of well-ordered signs is a real, secondary, instrumental cause of the knowledge a student comes to have, even while God remains, at the deepest level, the ultimate source of the very capacity for understanding that makes any learning possible at all.

The remaining articles. Aquinas goes on to ask whether a person can be called his own teacher, concluding that self-directed discovery, working through a problem on one’s own using the same basic movement from known to unknown, resembles teaching closely enough to be spoken of in an extended sense, though it lacks the strict social, other-directed character of teaching properly speaking. He considers whether angels teach human beings, extending the analysis to non-human rational agents, and whether teaching belongs to the active or contemplative life, situating the act of teaching within the broader framework of different forms of human life and their relative value that runs throughout his ethical and theological writing.

How to read it

Read article one on its own; it contains the treatise’s central argument and can be understood without the remaining three articles, which extend the framework to further, somewhat more specialized questions.

Read the medical analogy carefully and slowly. Aquinas’s comparison of a teacher’s causal role to a doctor’s role in restoring a patient’s health is doing enormous philosophical work in this text, and understanding precisely how a doctor is said to cause health without directly producing it the way fire directly produces heat is the key to understanding how Aquinas thinks a teacher causes knowledge.

Read Augustine’s own dialogue On the Teacher first if you can, even in summary. Aquinas’s question is explicitly framed as a direct response to Augustine, and seeing exactly what Augustine claimed, and how seriously Aquinas takes that claim before qualifying it, makes the structure of Aquinas’s own argument much clearer.

Notice the disputed question format itself as you read: Aquinas typically states objections to his eventual position first, often quite strong ones, before offering his own resolution and then responding individually to each objection. Reading the objections carefully, not skipping past them to get to Aquinas’s answer, gives a much better sense of what was genuinely at stake in the debate.

Test the account against your own experience of learning something difficult, whether from a teacher, a book, or working it out alone. Ask specifically whether Aquinas’s picture, that understanding is finally an act your own intellect must perform, however well-arranged the external signs and demonstrations that assist it, matches what actually happens when a difficult idea finally clicks.

Questions it raises

• Is Aquinas’s distinction between direct efficient causation and instrumental or mediate causation a real philosophical distinction, or is it a way of having it both ways between Augustine’s position and its opposite?
• If a teacher genuinely causes knowledge only by helping a learner’s own reason move from what it knows to what it does not, what happens when a learner lacks the prior knowledge a given piece of teaching presupposes?
• Does the medical analogy, comparing a teacher to a doctor assisting a natural healing process, actually capture what is distinctive about learning, or does it obscure important differences between physical healing and intellectual understanding?
• What follows for education if genuine understanding always requires the learner’s intellect to actively complete a movement the teacher can only guide and cannot guarantee?
• Aquinas affirms that God is the primary teacher while human teachers are genuine secondary causes. Is this compatible with everyday accounts of teaching that make no reference to God at all, or does the compatibility depend on accepting Aquinas’s larger theological framework?
• Can this account of teaching, developed for the transmission of demonstrable, reasoned knowledge, be extended to teaching skills, values, or practical wisdom, where the movement from known to unknown may not follow the same logical structure Aquinas has in mind?