According to Kant's deontological framework, the basis of moral reasoning is not to be found in anything empirical or contingent (such as human nature, social mores, religious dogma, tradition, individual dispositions, or even the consequences of our actions). It is, rather, to be found in the nature of practical reason itself: in the discovery of universal principles applicable to, and discoverable by, any and all rational beings (both in and out of this world).
Kant articulated his thoughts concerning morality most fully in his Critique of Practical Reason and in The Metaphysics of Morals, but he wrote a 'popular' introduction to his theory for non-experts, which many people consider a cruel joke, since they think the text is still impenetrable. Luckily, Nigel Warburton has decided to present Kant's ideas in a short and accessible format in the following audio clip based on his book Philosophy: The Classics.
And for more, check out the Kant tag .