Because a free will is not merely pushed around by external forces, external forces do not provide laws for a free will. The only source of law for a free will is that will itself. This is Kant's notion of "autonomy". Thus, Kant's notion of "freedom of the will" requires that we are morally self-legislating; that we impose the moral law on ourselves. Kant thinks that the positive understanding of freedom amounts to the same thing as the categorical imperative, and that “a free will and a will under moral laws are one and the same.” This is the key notion that later scholars call the reciprocity thesis, which states that a will is bound by the moral law if and only if it is free. That means that if you know that someone is free, then you know that the moral law applies to them, and vice versa. Kant then asks why we have to follow the principle of morality. Although we all may feel the force of our consciences, Kant, examining phenomena with a philosophical eye, is forced to “admit that no interest impels me to do so.” He says that we clearly do “regard ourselves as free in acting and so to hold ourselves yet subject to certain laws,” but wonders how this is possible. He then explains just how it is possible, by appealing to the two perspectives that we can consider ourselves under.