Full Idea
Laws, or what flow from them, are supposed to provide a unified explanation of the behaviours of particulars. Without universals the explanation of the behaviours of things lacks the required unity.
Gist of Idea
Laws cannot offer unified explanations if they don't involve universals
Source
Alexander Bird (Nature's Metaphysics [2007], 2.1.2)
Book Reference
Bird,Alexander: 'Nature's Metaphysics' [OUP 2007], p.18
A Reaction
Sounds a bit question-begging? Gravity seems fairly unified, whereas the frequency of London buses doesn't. Maybe I could unify bus-behaviour by positing a few new universals? The unity should first be in the phenomena, not in the explanation.