Justice is the first virtue of social institutions, as truth is of systems of thought. A theory however elegant and economical must be rejected or revised if it is untrue; likewise laws and institutions no matter how efficient and well-arranged must be reformed or abolished if they are unjust.
There are two kinds of comprehensive doctrines, religious and secular. Those of religious faith will say I give a veiled argument for secularism, and the latter will say I give a veiled argument for religion. I deny both. Each side presumes the basic ideas of constitutional democracy, so my suggestion is that we can make our political arguments in terms of public reason. Then we stand on common ground. That's how we can understand each other and cooperate.
Political philosophy is realistically utopian when it extends what are ordinarily thought to be the limits of practicable political possibility and, in so doing, reconciles us to our political and social condition. Our hope for the future of our society rests on the belief that the social world allows a reasonably just Society of Peoples.
When the basic structure of society is publicly known to satisfy its principles for an extended period of time, those subject to these arrangements tend to develop a desire to act in accordance with these principles and to do their part in institutions which exemplify them
The perspective of eternity is not a perspective from a certain place beyond the world, nor the point of view of a transcendent being; rather it is a certain form of thought and feeling that rational persons can adopt within the world ... Purity of heart, if one could attain it, would be to see clearly and to act with grace and self-command from this point of view.
Any comprehensive doctrine, religious or secular, can be introduced into any political argument at any time, but I argue that people who do this should also present what they believe are public reasons for their argument. So their opinion is no longer just that of one particular party, but an opinion that all members of a society might reasonably agree to, not necessarily that they would agree to. What's important is that people give the kinds of reasons that can be understood and appraised apart from their particular comprehensive doctrines.
Man is a historical being : The realisations of the powers of human individuals living at any one time takes the cooperation of many generations (or even societies) over a long period of time. By contrast with humankind, every individual animal can and does do what for the most part it might do, or what any other of its kind might or can do that lives at the same time.
Certainly it is wrong to be cruel to animals and the destruction of a whole species can be a great evil. The capacity for feelings of pleasure and pain and for the form of life of which animals are capable clearly impose duties of compassion and humanity in their case.