The mind is a conditioned object; and the mundane, "animal-speech" contents of the ordinary, un-enlightened human mind, are also conditioned. The mind is non-eternal; it is brought about through the cycle of birth and death. The brain is affected by physical substances -- pollution and nutrients, drugs, medicines, allergies and chemical side-effects. Vitamins, and the weather. It is affected by metabolic process, hunger, sleep, disease and aging, and by emotional stimuli as well; flattery, insults and the like. It is clearly not fully under its own control.
Just try to think rationally about, for example, paying bills, or any other mundane obligation, when you are hungry or tired. It's very difficult; it is easy for one's judgment to be impaired.
That doesn't even account for how one's emotions, preferences, opinions, and cravings are affected by misinformation and propaganda from others. How the mind feels about, for example, "my family" or "my romantic prospects" or "my career" or "my political party" -- all of one's biases are deeply influenced, intentionally and unintentionally, by the biases of others. One would have completely different views, if one was (mis)informed differently, and by different people.
Buddhism teaches that all thoughts of the self, by the self, are incorrect. Notions of "I am beautiful", "I am ugly", "I am moral", "I am wicked" and so forth are all based upon self-deception, and incomplete views of reality. One "feels" moral or wicked in the moment, without taking into account all the ways one can potentially be influenced in the opposite direction. (The Eight Winds/Eight Difficulties)
To the extent that "the mind" actually is "correct" and reliable, it is because it adheres to what is objectively true; when the mind decides that two plus two equals four, it decides this because that is verifiably true based upon the inescapable laws of arithmetic. Even the Buddha, when he reached Enlightenment, happened upon the laws of the dharma that had always been so; he did not own or invent anything. The Buddha had no intellectual property in the dharma--and neither does anybody else.
Anything true that the mind happens upon did not originate in the mind, but outside of it. And most of what is untrue also originated from what is outside of it.