And, generally, in the ages of Christian faith, it has been obvious and natural to hold that the realisation of virtue is essentially an enlightened and far-seeing pursuit of Happiness for the agent. Nor has this doctrine been held only by persons of a cold and calculating turn of mind: we find it urged with emphasis by so chivalrous and high-minded a preacher as Bishop Berkeley. No doubt this is only one side or element of the Christian view: the opposite doctrine, that an action done from motives of self-interest is not properly virtuous, has continually asserted itself as either openly conflicting or in some manner reconciled with the former. Still the former, though less refined and elevated, seems to have been the commoner view. Indeed, it is hardly going too far to say that common sense assumes that ‘interested’ actions, tending to promote the agent’s happiness, are _prima facie_ reasonable: and that the _onus probandi_ lies with those who maintain that disinterested conduct, as such, is reasonable. But, as has been before said, in the common notions of ‘interest,’ ‘happiness,’ etc., there is a certain amount of vagueness and ambiguity: so that in order to fit these terms for the purposes of scientific discussion, we must, while retaining the main part of their signification, endeavour to make it more precise. In my judgment this result is attained if by ‘greatest possible Happiness’ we understand the greatest attainable surplus of pleasure over pain; the two terms being used, with equally comprehensive meanings, to include respectively all kinds of agreeable and disagreeable feelings. Further, if this quantitative definition of the end be accepted, consistency requires that pleasures should be sought in proportion to their pleasantness; and therefore the less pleasant consciousness must not be preferred to the more pleasant, on the ground of any other qualities that it may possess. The distinctions of _quality_ that Mill and others urge may still be admitted as grounds of preference, but only in so far as they can be resolved into distinctions of quantity. This is the type to which the practical reasoning that is commonly called ‘Egoistic’ tends to conform, when we rigorously exclude all ambiguities and inconsistencies: and it is only in this more precise form that it seems worth while to subject such reasoning to a detailed examination. We must therefore understand by an Egoist a man who when two or more courses of action are open to him, ascertains as accurately as he can the amounts of pleasure and pain that are likely to result from each, and chooses the one which he thinks will yield him the greatest surplus of pleasure over pain.