The following is a reflection from some surplus notes to tonight’s reading for the Aquinas Seminar.
How do we pursue wisdom and attain truth? It is not an easy, simple, straightforward, linear task. It is a difficult, complex, windy, recursive process, wherein the chief obstacle is ourselves and our tendency to presume we know more of truth or more certainly that truth than in fact we do; this goes hand-in-hand with that presumption that our particular expertise or our specific knowledge qualifies us as wise in general. This attitude is antithetical to the exhortations Aquinas gives us in these chapters. Meditation upon the truth—the chief task of the person pursuing wisdom—is a lifelong endeavor. I have claimed previously that the background cosmological nihilism of our age is false; and the demonstration of falsity—particularly those falsehoods which keep us from fulfilling our nature as truth-seeking beings—the demonstration of falsity, Aquinas claims, liewibelongs also to the pursuit of wisdom. Thus we read, from Summa contra Gentiles, book 1, c.1, n.3 (translations from Anton Pegis):
It belongs to one and the same science, however, both to pursue one of two contraries and to oppose the other. Medicine, for example, seeks to effect health and to eliminate illness. Hence, just as it belongs to the wise man to meditate especially on the truth belonging to the first principle and to teach it to others, so it belongs to him to refute the opposing falsehood.
But refuting falsehoods, Aquinas says, is no easy task. I will direct your attention generally to c.2, n.3, but especially the first paragraph and especially the text in bold:
To proceed against individual errors, however, is a difficult business, and this for two reasons. In the first place, it is difficult because the sacrilegious remarks of individual men who have erred are not so well known to us so that we may use what they say as the basis of proceeding to a refutation of their errors.
The unknown remarks of those who have erred; here, Aquinas is concerned specifically with those which go against the truth of faith, but this difficulty is universal in refuting any kind of error. To refute an error, in other words, one must know what the error is. In many ways, this is the most difficult aspect of forming a good philosophical habit: namely, trying truly to understanding what the other says, particularly if our immediate goal is defense of something we believe is true. I would go so far as to say it is much more difficult in our own day than in Aquinas’, for the number of errors is much greater, more complicated, and there lies a much deeper history or intellectual tradition behind many of the errors.
Yet we can still learn from Aquinas. As he goes on:
This is, indeed, the method that the ancient Doctors of the Church used in the refutation of the errors of the Gentiles. For they could know the positions taken by the Gentiles since they themselves had been Gentiles, or at least had lived among the Gentiles and had been instructed in their teaching.
…We must, therefore, have recourse to the natural reason, to which all men are forced to give their assent…
This does not mean everyone will debate with us according to natural reason and in good faith. Most people likely will not; not necessarily because they lack a desire for truth, but because bad intellectual habits have been inculcated through immersion in a truth-less society. When we speak to them in terms they understand to signify something else, or in terms of which they have no comprehension whatsoever, while they likewise speak to us in terms they do not know, we come to impasses of mutual incomprehensibility and discussion becomes an impossibility.
 Ibid, n.3: “Eiusdem autem est unum contrariorum prosequi et aliud refutare sicut medicina, quae sanitatem operator, aegritudinem excludit. Unde sicut sapientis est veritatem praecipue de primo principio meditari et aliis disserere, ita eius est falistatem contrariam impugnare.”
 Ibid, c.2, n.3: “Contra singulorum autem errores difficile est procedere, propter duo. Primo, quia non ita sunt nobis nota singulorum errantium dicta sacrilega ut ex his quae dicunt possimus rationes assumere ad eorum errores destruendos. Hoc enim modo usi sunt antiqui doctores in destructionem errorum gentilium quorum positiones scire poterant quia et ipsi gentiles fuerant, vel saltem inter gentiles conversati et in eorum doctrinis eruditi.
“Secundo, quia quidam eorum, ut Mahumetistae et Pagani, non conveniunt nobiscum in auctoritate alicuius Scripturae, per quam possint convinci, sicut contra Iudaeos disputare possumus per vetus testamentum, contra haereticos per novum. Hi vero neutrum recipiunt. Unde necesse est ad naturalem rationem recurrere, cui omnes assentire coguntur. Quae tamen in rebus divinis deficiens est.”