Great insights into Maran HaRav's educational philosophy can be gleaned from the following letter he wrote in 1906 (Iggeret 43, Translation by Rav Bezalel Naor):
By the grace of God, the holy city of Jaffa, may it be built and established, 12 Kislev 5666.
Peace and blessing to the venerable great Rav, our teacher Yeshayahu Orenstein, may his light shine. Your precious letter reached me, and I had some doubt whether or not to reply, because I feared that you, heaven forbid, would suffer anguish from my letter, and why should I cause a venerable Torah scholar such as yourself, long life to you, any suffering? In any case, I decided to answer briefly, [and] perhaps the Lord, blessed be he, will grant that you heed my words, so that you may suffer less pain from the [issues dealt with in my] articles, and this will be my reward — saving a precious soul like yours from pain and worry.
You should know, your honor, that my main intention In my articles, and with anything I write, is simply to awaken the hearts of Torah scholars, old and young, to diligence in the careful study of the inner Torah [in all the following ways]: in mussar in all the ways we have received from our most holy teachers; in the [philosophical] investigation of all the holy books left to us as a legacy by our great Rabbis, masters of inquiry; in kabbala in accordance with all the ways which are an inheritance from our fathers, may their memory protect us: in the way of the Rishonim; of the Achronim; [The Rishonim and Achronim are the early and later generations of Torah scholars in medieval Europe. Rav Kook is referring specifically to the early mystics, such as Nachmanides and Roke’ach, and the later ones, the Ari and his disciples.] of Chassidism; and of the Gaon Rav Eliahu from Vilna and Rav Moshe Chaim Luzzato, of blessed memory. And [also] to study all the commentaries on the holy Zohar, and Sifra Detzinuta, Sefer Habahir, and the Book of Creation, and all the midrashim of our sages, [with the purpose of gaining] both familiarity and expertise. This demands great diligence, just like the diligence needed for the study of the Talmud and legal rulings.
True, not everyone's nature is fit for this, so anyone who is unable, but who is of keen mind, is obligated to study at length the intricacies of the Talmud, the commentaries of Rashi and the Tosefot on it, and the legal rulings [of great rabbis]. One, however, who has talent for the in-depth study of wisdom and kabbala should shorten his lengthy periods [of legalistic study of the Talmud], even though the intricacies and innovation [of Talmudic and legal studies] require them. In any case, he must not neglect the study of the intricacies of the Torah, because God finds joy in it.
The major part of his study, however, should be to know his creator. This is written in the introduction to Etz Chaim, and see also Or Ne’erav. In these times, when because of our many transgressions, many young people are becoming more and more enticed by the smooth [cosmopolitan] speech of the nonbelievers in our nation, we must also show the world that Torah scholars occupied in the holiness of the true Torah not lack power of rhetoric and eloquence of language.
This was the intention of the pious Rav Moshe Chaim Luzzato of blessed memory, in his poetry and [drama]] and I, in humility, also want to grasp the hem of their cloaks and follow their example inasmuch as I am able. And because the full [comprehension] of the Holy Torah also requires the knowledge of the wisdom of the world in some matters, and in particular so as to be able to reply to a nonbeliever, an imperative in our day.
For this reason I mention the words of our Rabbis, the Gaon Of Vilna and the Maharal of Prague in his book Netivot Olam, [section] Netiv Hatorah, chapter 14.8 [It must, however, come only after] diligent study of the Torah and the purification of virtues and deeds, especially from anger, arrogance, and sadness, which are the major causes of evil, and the diligent, fixed, and daily study of the inner Torah, each person according to his capabilities.
From examination and experience [we know], after all these preliminaries, that one can not be harmed, heaven forbid, from the knowledge of [secular] wisdom, if taken in measure and with the [earnest goal] of honoring God; on the contrary, it will add to one's strength great happiness and broadness of mind in the service of the Lord, blessed be he.
And if, heaven forbid, there are people who misunderstand my words, and see in them meanings I did not intend, this is not [sufficient reason] to keep the benefit [of my words] from those worthy of it, as Maimonides, of blessed memory, wrote in his letters, that the ways of the Lord are trustworthy, etc.
Through diligent regular study in the pleasure of the inner Holy Torah, the soul which occupies itself with this without seeking any personal benefit will be lit in the light of happiness and most sublime love, spiritual pleasures like those of the world to come, and there will be no need to fear the evil lash, or only to a minimal extent, and with this one's soul will find strength and courage, and fear no adversity, not in this world and not in the next, for even if sit in darkness, the Lord is my light.
This is, approximately, the intention of the words of mine on which you commented. How good and pleasurable it is to judge one another favorably, and by this the heavens are praised and the honor of heaven magnified, as is the honor of the Holy Land and the Torah scholars in it.
As for myself, I take no great delight at being praised, nor offense at being insulted. Praise the Lord's blessed name, that diligent occupation with the study of mussar and the inner Holy Torah granted me this characteristic. For this reason, I see no need on my part to explain myself. I do so simply to calm your heart so that you will not suffer, because all my will and desire is to bring happiness to people and fulfill, as much as I can, "those who fear you will see me and rejoice.’’ For this reason I said that I hope that these words may pacify your heart. And may the Lord blessed be he, bless you and your family with long life, and may we be privileged to see the joy of Zion and the building of Jerusalem with the revelation of the majesty of his blessed kingdom, a name for us, praise in all the nations of the Land, and may the entire Land be filled with the knowledge of the Lord. As is becoming your pleasant soul, and the humble young soul on your doorstep, looking to light and salvation.
Avraham Yitzhak Hakohen Kook