What's Rav Kooks understanding of Kefira (lack of belief)?

The questioner mentioned Rav Kooks understanding of Kefira. Can you please explain it and provide sources? Thank you!

Rav Kook wrote a lot on the topic, much more than we can encompass in the scope of this short framework. In short, Rav Kook says that as opposed to the apostates of old, who’s kfira against Judaism was to leave and be paganist or Christian (usually in order to survive or raise their standard of living), today, all kofrim are atheist, and if they’re honest, admit that they don’t know 100% for sure, and can’t prove that there definitely isn’t a G-d, chalila (what you’ve never (!) seen or don’t understand is not a proof of anything, especially regarding something which by definition, can’t be comprehended). Additionally (and this is what the previous question related to), the kfira today is often a result of a wrong, childish and frightening mistaken image of some “power-hungry” god, who enjoys telling us what to do and what not to do. This is an egoistical and far-from-perfect god, which a true believer should also rebel against. Such a belief does more harm than good, and the rebellion against it is a positive one, which will enable the real, deeper, loving, and beautiful belief to be built, upon the ruins of the false images of god. He explains that part of the misunderstanding, stems from what the yeshiva world invests almost all their time on learning Talmud, and neglects the study of Rambam, Kuzari, Maharal, Chasidut, Kabbala, and other Jewish classics of philosophy and faith, intellect and emotion. The leaving of the shtetl exposed Jews to the modern and post-renaissance world, broke the monopoly that religion had on the Jews, and the subsequent kfira forces the rabbis to re-discover the deep, appealing and richer variety of Torah, in order to “compete” with the other contending ideologies. We have no doubt that the truth and ideals of the perfect Godly Torah will convince. [See Mishna Sotah (9, 15 B'Ikvot Mashicha...); Ma'amarei HaReiya, p. 234-235; Ikvei HaTzon, pp. 108-116, 137, 145].