A person who already displays … cruelty to animals is also no less hardened towards men. We can already know the human heart, even in regard to anima… - Immanuel Kant

What then is it which justifies virtue or the morally good disposition, in making such lofty claims? It is nothing less than the privilege it secures to the rational being of participating in the giving of universal laws, by which it qualifies him to be a member of a possible kingdom of ends, a privilege to which he was already destined by his own nature as being an end in himself, and on that account legislating in the kingdom of ends; free as regards all laws of physical nature, and obeying those only which he himself gives, and by which his maxims can belong to a system of universal law, to which at the same time he submits himself. For nothing has any worth except what the law assigns it.

Experience without theory is blind, but theory without experience is mere intellectual play.

Duas coisas enchem o ânimo de admiração: o céu estrelado acima de mim, e a lei moral dentro de mim; ambas não estão fora do meu horizonte; antes, vejo-as perante mim e religo-as imediatamente com a consciência de minha existência. A primeira começa no lugar que eu ocupo no mundo e no exterior. A segunda começa no meu invisível eu, na minha personalidade e me coloca num mundo que tem a verdadeira infinidade; o que eleva infinitamente o meu valor como inteligência na qual a lei moral me revela uma vida independente da animalidade de todo mundo sensível.