Malbim: "Ki Yetzer Lev ha'Adam Ra mi'Ne'urav" (Bereishis 8:21). The pictures of the heart lean towards desire, and the opposite of the laws of Chachmah. He must go according to the laws of Chachmah - via this, he will be saved from being trapped in images of his heart. One who trusts in his heart, to go as his heart will lean, based on its evil images, he is a Kesil. A Kesil is estranged from the laws of Chachmah, due to his desires. He does not desire Tevunah, rather, openness of his heart ¹ . One who goes in Chachmah, he is saved from the evil images of the heart. Chachmah leads him on calm waters, to fight against the Yetzarim of the heart.