Social Justice is a term awash in political and religious associations. The National Association of Social Workers (NASW) has the best definition. It is reasonably concise and lacks political or religious baggage:
Social justice is the view that everyone deserves equal economic, political and social rights and opportunities.
When seen in this simple light, shorn of its religious and classist imperatives, social justice conforms to our post-Enlightenment biases. Few could disagree that in a truly free society, "everyone" deserves to be treated equally and equally offered the fruits of humanity's efforts. It is when we talk about altering the world in a way as to bring reality more in line with the ideal that the difficulty of implementation tempts us to dismiss social justice as hopelessly Utopian.
Many powerful people face a loss of privilege and influence in a world of equality, many of the less fortunate yearn not so much for a world of equality than a world in which they are the powerful. Trading one uncaring master for another matters little, unless the master or master-to-be is you.
Humanism rejects the notion that God or gods are due allegiance or concern, and Humanists choose to concentrate their efforts on the concerns of human beings alive in the here and now. To a Humanist, then, creating a just world of equal rights and opportunity for all persons is the only true consideration.
Whereas the religious must use sometimes torturous theology to get get from a God of Old Testament wrath to a philosophical position concerned with the plight of our fellow persons, Humanists begin with the plight of our fellow persons. We never worry about the supernatural world because the natural world is challenging enough, and, we do not believe in supernaturalism.
Humanism's commitment to science, philosophy and truth means that some doctrines, no matter how beguiling they might appear, must be rejected if shown to be not in accordance with our observations of the world. Our lack of religious faith is a strength: there is no law greater than those found in nature and therefore no reason to violate our conscience to appease some ancient mythological God. Humanists are free to love and support our LGBTQ brothers and sisters despite the New Testament, we are free to see women as equal members of society despite the Koran, and we are free to accept the findings of science despite Genesis.
Many, many non-Humanists get to the same page as Humanists when it comes to social justice. They have a faith rooted in Jesus or Muhammad or some ancient book or belief that brings them ultimately to the same convictions as Humanists. Humanists may be tempted to say that these people took the long way to get to the same place, but in truth we are all at this moment in time in exactly the same world and at the same time. There are no winners or losers in the game of getting our philosophies right. What matters is that we have allies with whom to pursue our goals of social justice.
But there are dangers in working with religious allies. Religious systems of social justice are built on foundations of mythology, and a Catholic partner on immigration reform, for instance, may not be by the side of a Humanist compatriot when it comes to reproductive justice or LGBTQ rights. The religious have established their philosophy and sense of social justice on God first, persons second.
The power of Humanism is that we put persons first, and since it has been shown time and again that people flourish in a world of equality and opportunity, there can be no Humanism without a commitment to social justice.