"My manner of thinking, so you say, cannot be approved. Do you suppose I care? A poor fool indeed is he who adopts a manner of thinking for others!"

The Marquis de Sade is expressing his disdain for those who try to dictate how he should think. He is asserting his independence and autonomy, and is not willing to conform to the expectations of others. He is making it clear that he will not be swayed by the opinions of others, and that he will think for himself. He is also implying that those who try to control the thoughts of others are foolish. He is emphasizing the importance of individual autonomy and freedom of thought. He is asserting that no one should be forced to think in a certain way, and that everyone should be allowed to think for themselves. He is asserting that it is wrong to try to control the thoughts of others, and that everyone should be allowed to think freely.