Works for me. Would more unmeasurable things like love, hate, good or evil come from the same type of higher dimension (higher in terms of 5th, 6th, etc)?
I think what I see as good projects from Buddha-nature, but that what is unvirtue is due to illusion and ignorance. It is akin to Plato's notion that evil cannot have it's own reality, because it is by nature- a distortion or wrong application of good.
Okay, essentially the way I see the inability of compassion to be measured is this: any human measurement is just that. Any conception of a measurement is a human conception. Buddhists see higher truths as paradoxical. They escape human explanation.
The reasoning behind Koans, such as: 'what is the sound of one hand clapping'? Is to get a person beyond the conceptual. Yet in the Buddhist worldview, the virtues actually exist. They are part of the Buddha's immeasurable activity. Obviously I mean the cosmic Buddha here, the essential core of everything's nature in Mahayana view.
When you act in compassion, you're acting from that nature, so it cannot be measured in human units. The Holy Teaching of Vamalakirti, one of the Mahayana scriptures- describes it like this: that the Buddha's action is the generation of a Bodhisattva field. That when you act in accordance with the truth, it is though the Buddha were acting. You are part of the Buddha generating meritorious fields, when acting without poisons like selfishness.
I hope I'm not getting too technical here. If I am, I'll try to explain it better if you point it out to me.
To emphasize the inability of humans to truly grasp a thing like compassion- compassion and it's cultivation is one of the four immeasurables. The four immeasurables are said to be the blessed marks of a deity nature, which short of being a Buddha- is the best nature. Divine beings are naturally marked with this disposition to pity everything that is mortal, and want to help the best one knows how.
We are told to cultivate these immeasurables as practicing Buddhists. If one didn't want to see it literal- that the god nature is marked with compassion inborn> one could say it's to demonstrate how beyond the human scope and heavenly good deeds are.