In connection with Michtav M’Eliyahu (“Strive for TRUTH!” vol. I, THE ROOTS OF MUSSAR).
Reason maintains coherence through being a self-contained process, or, in other words, pursuing the truth for its own sake because it is true.
Any external reason to care about the conclusion of your thoughts is called a bribe.
A bribe influences the conclusion of a line of thought away from the truth.
An animal cares about its thoughts because they help it preserve its body.
Man is thus least an animal — least bribed by his temporal/spatial body — when he thinks but is totally indifferent to the conclusion of his thoughts, i.e. when he thinks abstractly.
Thought is therefore less bribed and more likely to be true the fewer bodily needs we feel and satisfy.
However, once we think with total detachment, we no longer feel ethically compelled to act by the conclusions of our thoughts, for we are detached from them.
In a state of pure, detached reason, the only ethic is the internal coherence of the truth. Without a state of pure, detached reason, the only ethic is the bribery of the body.
In the state of total intellectual detachment, there is no ethics.
But only in a state of total intellectual detachment can there be ethics.
The solution to this contradiction is faith, which through identity provides an ultimate reason to care about the conclusion of our thoughts.
“This is wrong,” they tell Aristotle, and he may always reply that he is not, at the moment, Aristotle, because he is not thinking abstractly, and no abstract thought can ever, on its own, compel him to act differently.
“This is wrong,” they tell a Jew, and he can never not be a Jew, for he is compelled not by his own understanding but the G-d who creates him and makes him what he is from the inside.
So: One can only really think if one is a mensch, a human being in the fullest sense. But reason and judgement are themselves limited and cannot form the basis of our ethics.
It’s not that we must be menschen in order to think (though this is also true), but that the entire purpose of thought is simply to internalize and unite with our (axiomatic, faith-based) menschlichkeit, which is part of who we are, as the chosen people of G-d, one with His holy Torah.