https://www.philosophyofreligion.uk/theistic-proofs/the-cosmological-argument/the-argument-from-contingency/is-the-universe-contingent/contingent.
The Fallacy of Composition
This argument has been accused of committing the fallacy of composition. The fallacy of composition is the fallacy of inferring from the fact that every part of a whole has a property, that the whole has that property too.
In some cases this kind of inference looks better than in others. If every jewel in a crown is valuable, then the crown is going to be valuable too. If every player on the team is outstanding, then it’s likely, though not certain, that the team is outstanding too.
If every track on the CD is less than five minutes long, though, then it doesn‘t follow that the whole CD is less than five minutes long. Sometimes every part of a whole has a property that the whole itself does not have.
So does the contingency of every part of the universe imply that the universe as a whole is contingent? Apparently not. For in order for the universe to be necessarily existent, it need only be the case that there must exist something rather than nothing; it need not be the case that anything in particular must exist, just that at least one of the many things that might exist must exist, no matter which one it is.
A necessary universe might therefore be composed entirely of contingent parts. The contingency of the parts of the universe therefore does not imply that the universe as a whole is contingent. It might be that even though every part of the universe is contingent, the universe itself is not. It might be that even though it is not necessary that the universe exist in one particular form rather than in any other, the universe had to exist in some form; it could not have failed to exist altogether.
The argument from the contingency of the parts of the universe, then, may not establish that the universe itself is contingent. However, the idea that the universe is necessary rather than contingent does seem to suspect.
To say that the universe is necessary is to say that its non-existence is impossible. Most impossibilities are easily recognised because they involve obvious logical contradiction. The existence of a square circle is impossible, because the idea of a square circle is self-contradictory.
Where, though, is the logical contradiction in the idea of the universe not existing? There seems to be none; the universe does appear to be contingent.