In one of the most stirring passages in modern ethics, Immanuel Kant famously enjoins: "act that you use humanity, whether in your own person or in the person of any other, always at the same time as an end, never merely as a means." Precisely what Kant means here, however, is not entirely clear. More than one interpretation of this formula is possible. But the importance of Kant's "formula of ends" in modern moral philosophy is impossible to deny.