Why Should I Listen to My Conscience? Equity and the Question of Ontological Obligation

What is it about obligation that obligates us? Is it possible to answer this question whilst remaining within the sphere of obligation as obligation; that is, without resorting to external justifications of why it is better to obey obligations than not to? It is at the very least arguable that, for the most part, obligation is only a secondary and derivative concern for modern law. Obligations are often constructed negatively by means of proscription (I am obligated not to act dangerously). Or else they derive from the atomistic entitlement inherent in modern legal subjectivity (I am obligated to honour my freely made agreements). Or sometimes by a combination of both (I am obligated to respect others’ property rights, for example).