If we are thinking of other moral agents, duty prescribes strict and unfailing justice; and justice in its highest and purest form is love, the unfailing recognition of the fullest claims that can be made on us by all who share our own divine superiority:  to love God above all else, and to love all spiritual beings as we love ourselves, this is duty in relation to other spiritual beings.

If we are thinking of creatures which, whether moral agents or not, are capable of pain and pleasure, our duty takes the form of goodness or tenderness.  We have no right to inflict pain or even refuse pleasure unless, if the circumstances were reversed, we should be bound in conscience to be ready in our turn to bear the same infliction or refusal.  The precept, Do as you would be done by, is here supreme, and it is to this class of duties that that precept applies, and the limits of our right to inflict pain on other creatures, whether rational or irrational, will be determined by this rule.

And, lower still, our duty to things that are incapable of all feeling is summed up in that knowledge of them and that use of them which makes them the fittest instruments of a moral life.

The sentiment of reverence is our guide in determining our duty, and the test of universality perpetually comes in to correct the commands of this sentiment and to clear and so to refine the sentiment itself.

As is the case in a certain degree with every other kind of knowledge or belief, so in a very special degree the Moral Law finds its place even in minds that have very little of thought or of cultivation.  The most untutored is not insensible to the claim made on our respect by acts of courage, self-sacrifice, generosity, truth; or to the call upon us for reprobation at the sight of acts of falsehood, of meanness, of cruelty, of profligacy.  Even in the most untutored there is a sense that these sentiments of respect and reprobation are quite different in kind from the other sentiments which stir the soul.  And this is even more clear in condemnation than in approval.  However perverted the conscience (the seat of these sentiments) may be, yet the pain of remorse, which is self-reprobation for having broken the moral law, is always, as has been well said, ‘quite unlike any other pain we know,’ and is felt in some form and measure by every soul that lives.  And as the sentiment thus holds a special place in the most untutored, so too does the sense of universality by which we instinctively and invariably correct or defend that sentiment if it be challenged.  The moment we are perplexed in regard to what we ought to do or what judgment we ought to pass on something already done, we instinctively, almost involuntarily, endeavour to disentangle the act from all attendant circumstances and to see whether our sentiment of approval or disapproval would still hold good in quite other surroundings.  We try to get, at the principle involved and to ascertain whether that principle possesses the universality which is the sure characteristic of the Moral Law.