 The principles themselves, it should be remembered, are self-evident; and to conclude the contrary … because of the obscurity attending several cases wherein a competition arises between the several principles of morality, is very unreasonable. It is not unlike concluding, that, … because it may not in some instances be easy to determine what will be the effect of different forces, variously compounded and acting contrary to each other; therefore we can have no assurance what any of them acting separately will produce, or so much as know that there is any such thing as force. (R 168)