This reminds me of David Hicks' argument for dogma, in Norms and Nobility. I don't have my copy handy to quote from, but he makes this same point--that the starting place for learning to think and argue is acceptance or belief in something. I think the underlying nugget of truth behind the idea might be that by believing something, we are giving intellectual assent at a deep level to the idea that there is Truth at all. In general, our culture rejects the idea of absolute truth--it's all relative. There's "your truth" and "my truth," but nothing solid and universally True, and this idea of little-t "truths" which don't apply to everyone gives young people the hopelessness which arises when there is no Truth (even when they don't or can't express it clearly). By embracing a dogma--even if it has to be corrected and refined by questioning or further learning--you are actually embracing the idea that capital-t Truth exists, and that makes an enormous difference in intellectual and spiritual growth.
I believe it was in my recent reading of The Liberal Arts Tradition that I was struck by something quoted about grammar... Okay, I found it on my blog--forgive me for quoting a bit of my blog post here:
It would be so, so easy to gloss over that while reading this book, but you shouldn't. You really shouldn't. Without reading a word further, you should stop right there and think for a while about why that would be so. Why would "believing" in grammar support a belief in God---make it difficult to "get rid" of God? Just working out a hypothesis for that yourself will alter your perspective of grammar forever, I think.
Speaking of grammar, Charlotte Mason wrote:
It requires some effort of abstraction for a child to perceive that when we speak, we speak about something and say something about it; and he has learned nearly all the grammar that is necessary when he knows that when we speak we use sentences and that a sentence makes sense; that we can put words together so as to make utter nonsense, as,--- "Tom immediately candlestick uproarious nevertheless"---a string of words making perfect nonsense and therefore not a sentence. If we use words in such a way as to make sense we get a sentence; "John goes to school" is a sentence. (Philosophy of Education, p. 209)
Why do you suppose Charlotte Mason says that is "nearly all the grammar that is necessary"? (In practice, her students learned more detail than that!) I think it is because it cuts to the heart of language and reveals the inherent structure of language, without which there could be no communication at all, no sense. It is the very logos of language, not of English alone, but all language. And that is why Nietzsche fretted about grammar making it difficult to dispense with God, who alone could create such an order, such a law, like the law of gravity, which no one can break. There are different types of grammar, but they share certain inherent properties, for which I refer you to Augustine. A noun is a noun in any language, and it may be that the contemplation of noun-ness rather than memorizing a definition and identifying random nouns is what makes grammar a university-level art.
I quote all of that just to underscore my agreement with the idea that teaching the liberal arts as arts is the best foundation for thinking, and "critical thinking" is probably a misnomer.