Obj. 1 - All the creatures that God made were good therefore there is no need for purification
Resp. 1 - perfection of creatures considered in 2 ways
a) regarding their substance : creatures are simply good and therefore not in need of purification
b) as mixed with foreign nature which is inconsistent with its perfection : evil becomes accidental to creature this therefore needs purification
Obj. 2 - Purification is to take away uncleanness of fault but fault does not infect elements of world
Resp. 2 - The elements become the subject of fault by being used to commit the fault therefore they are not suited to to receive glory till this be taken away.
But in Scripture we see:
Apoc 21,1 and II Pet 3,10-13 speaks of a renewal of heaven and earth which implies a certain purification
Conclusion
The World which is the means for man to attain heaven, it also should attain to a better state when man is glorified by his body. Just as man attains glory by purification from corruption and faults, by suffering here or in Purgatory, so the elements of world must be purified from all contrary dispositions (due to bad use made of them) which produce in them a certain unsuitability to be glorified.