It's subjective as in: imagine a different society/species constructing a sense of reality and computation, based on liquid mixtures. Their basis of computation, their axiom is 1l of alcohol + 1l of water = 2l of mixture.

They meet us, and we exchange ideas.

They go: of course 1 + 1 = 2, look at our mixture. For fruits, apples and pears? That's outside of normal arithmetics, it's an exception. There's no + there, as you're not mixing. You have to correct for the non mixture nature, the answer will be larger than 2.