Unless our ethics are grounded in the person and work of Jesus Christ, they will either fluctuate from one extreme to the other. On the one extreme our ethics will become so divorced from any concrete grounding that they will become completely relativized. Ethics in this scenario becomes entirely culturally conditioned and has no center. On the other hand, if our ethics has a center apart from the person and work of Christ, even if biblically based, then it becomes too concrete and cannot adapt to the vast variety of cultural contexts spanning human history. That kind of ethics ends up becoming a one size fits all model that forces the facts on the ground to be twisted and contorted in order to fit them into that rigid system.
In contrast to these two extremes, Christ and cross centered ethics offers up a grounding of ethics in the life lived by Christ as our model exemplar. Even the previous revelation given to the Israelites through the law of Moses is seen in a new light because of Christ's incarnation. He both fulfills the law, thus satisfying its demands, but also gives an even higher standard than what the law called for as taught by Moses and the rabbis.
But finally, Christ on the cross gives us a full grounding of our ethics in a way that no other system can ever give. The reason for this incomparability is because Christ on the cross isn't a system, it's a person, God the Creator, entering into history through the person, Jesus of Nazareth, in order to redeem an estranged creation. All of history, whether human or otherwise, is impacted by this radical intervention by our Creator God. No part of creation is exempt from this and thus everything has ethical implications, whether our personal ethics, our political ethics, our economic ethics, or our environmental ethics, which includes both our interactions with the animal and the plant world.
As creaturely beings, along with the rest of creation, we have been radically impacted by this intervention by God through Christ Jesus. God began the work of restoration with Christ's resurrection. It will find its consummation with his return when all things will be made new. That day is not yet here, but we have been given a model in Christ's life, death and resurrection. We partake of his kingdom work when we enter into the mystery of his sacrificial life and death, knowing that we live because he died and lived again. The women and men who surrounded him during his ministry, and whose eyes were opened to who he is, were radically transformed by this new reality. They went from hardened disbelief and arrogance to living lives of self sacrificial service to each other and to all around them. This transformation in their lives proved to be more powerful than anything Rome or Jerusalem could ever wield. That is the same transformation that we have available today if we would only see him for who he is and what he has truly affected.