As its name suggests, progressivism wants to make progress. This would seem to mean that it wants to achieve new things that are good, and leave behind old things that are bad. Who wouldn’t be for that?
But to know whether you are making progress or not, you need an objective standard of what is good. In short, you need the natural law.
The problem is that natural law is one of the things progressives want to get rid of. They consider belief in natural law reactionary, because they think all principles of morality and justice are subject to change. You do whatever works.
But in this case they are trying to progress beyond the very standard by which progress can be gauged.
For without an objective natural law, progress cannot be distinguished from regress. You can’t even distinguish what “works” from what doesn’t. There is only meaningless turbulence and purposeless alternation, according to the whims of the moment.
You might, of course, try to rescue progressivism from incoherence by saying that whatever is, is good and right. This would imply that whatever change is taking place at this moment is good change, just because it is happening. And it would imply that whatever you are doing to make it happen, is right to do, just because you are doing it.
But that wouldn’t really rescue the cause of progressivism, because it would also imply that whatever isn’t changing right now, shouldn’t change, just because it isn’t. And it would imply that whatever your opponents are doing to make a different thing happen, is also good to do, just because they are doing it.
If you really throw out any objective standard of good and evil, then you have no reason to do anything at all – nor have you any reason not to do anything at all. You have no more reason to feed the poor than to starve them, no more reason to champion justice than tyranny. You have no reason to live, but you have no reason even to commit suicide.
You might also try another way of rescuing progressivism from incoherence. You might say that whoever wins is right. And you might do whatever it takes to win, because then winning would make you right. That describes a lot of progressivism pretty well.
But in this case, you haven’t escaped from belief in an objective morality after all. You have merely tumbled into the belief that the one and only thing that is ultimately right and good is power over others.