Note: This is not to suggest that abstract things are outside space and time, at least not in a literal sense. For they could only be outside something (taken literally) if they had a spatial location, and it would be contradictory to suggest that they have no spatial location and are outside space and time.
Some possible replies:
If the first premise here is contentious, then we could start with the premise that it is true that 2 + 2 = 4, which has to be the least contentious premise we could come up with.
But need physical laws be true? Even if they are, why do there have to be numbers and functions for them to be true? Perhaps they can be formulated without any appeal to numbers or functions.
We could even take them to be various concrete things, as long as they stand in the right relations to each other. So perhaps numbers are concrete things.
But laws of nature support counterfactuals: If I were to place this heavy object in water then it would sink; Why? Because heavy objects sink in water. The present proposal seems to not account for this.
If this is right, and if the law is true, then there are properties. And if properties are abstract, then there are abstract things.
But Lowe raises a question for this approach to laws: Why should the particulars obey the law, if it is a relation between properties?