Immanuel Kant,
The Metaphysical Elements of Ethics
“ Accordingly, this duty to estimate the worth of one's actions not merely by their legality, but also by their morality (mental disposition) , is only of indeterminate obligation; the law does not command this internal action in the human mind itself, but only the maxim of the action, namely, that we should strive with all our power that for all dutiful actions the thought of duty should be of itself an adequate spring. ”
