Now (second), a principle that is based only on the subjective condition of receptivity to a pleasure or displeasure a receptivity which can always be cognized only empirically and cannot be valid in the same way for all rational beings) can indeed serve the subject who possesses this receptivity as his maxim, but it cannot serve even the subject himse as a law (because it is lacking in objective necessity, which must be cognized a priori); and hence such a principle can never provide a practical law.