I think the point--though perhaps not expressed clearly enough--is that our existing models of physics are adequate to explain all phenomena reductively--in principle, albeit not in practice. There is very little that doesn't work the way we think when we isolate the fundamental interactions.

The problem lies in predicting the consequences of those actions, which isn't a solved problem at all, and so most of science needs to deal with phenomena at the level of description that we typically use for them.

I don't think Young's description denies emergent properties, though I don't think it makes it all that clear just how huge the gulf is between understanding, say, virtual particles and being able to work usefully with, say, glucose homeostasis in the liver.