As a consequence of his monistic philosophy, Schopenhauer was very concerned about animal welfare. For him, all individual animals, including humans, are essentially phenomenal manifestations of the one underlying Will. The word "will" designated, for him, force, power, impulse, energy, and desire; it is the closest word we have that can signify both the essence of all external things and our own direct, inner experience. Since every living thing possesses will, humans and animals are fundamentally the same and can recognize themselves in each other. For this reason, he claimed that a good person would have sympathy for animals, who are our fellow sufferers.