AND WHAT SHOULD ONE INVESTIGATE IN ONESELF BEFORE ADOPTING THE VIEW THAT ONE SHOULD INVESTIGATE THE DAILY LIVES OF "THINKERS" BEFORE ADOPTING THEIR VIEWS?
One should actually investigate the daily life of a thinker before adopting their views, because it’s impossibly to separate the art from the artist or the thoughts from their thinker.
Assuming the green text is true, Kant’s moral theory is downstream from his own morals. We can see this in other so-called “philosophers.” Nietzsche and Descartes for example.
Descartes was a deeply feeble man, relegated to his chambers for much of his life. Being well-to-do, he possessed servants to cater to his needs, but rarely was he able to do this on his own. It comes as no surprise then, that he would develop his mind-matter theory. His entire life was about things happening to him, and his only way of internalizing it being through his thoughts.
Nitezsche, conversely, is an author defined by contradiction. Born a paraplegic and a lover spurned by his deepest attachment, he writes of strong men acting on their own whims and actualizing their passions for their own sake.
Likewise does he deride the ancient philosophers for arguing and writing their wisdom… while doing the very same thing. He does this perhaps because he resents himself and the lot that life chose for him.