Justice is what God expects of us. Justice is the standards he holds us to.

The standards he holds us to are impossibly high. We cannot satisfy justice.

Why?

Most of the time we just take the standards for granted.  Justice is what it is.  But why couldn’t God simply expect less of us? That may have been what Satan was advocating for in the Council in Heaven.

Maybe “justice” isn’t just what it is.  In fact, if we started from zero, we would have to conclude that natural justice would be standards that we could reach. That would be real justice. The existence of standards that we always fails cannot be just.

But God loves us. If we only satisfied the demands of natural justice, we wouldn’t deserve more than natural happiness. We would not even be capable of more. But God loves us. He wants more for us. So he sets standards based not on what we can achieve but on what he wants us to achieve.

Setting standards higher than natural justice permits is only just if the standard-setter agrees to make up the difference. So God agreed to make up the difference. Hence the atonement.

So mercy—the atonement—doesn’t defeat justice. Of course it doesn’t. Mercy is what makes justice just.

Love is where both our justice and our mercy come from.