Atheism may posit an infinite series of causes to account for the existence of contingent substances, motion, or change. If an infinite series is posited, that series is also subject to the problem of passive potency inferring an extrinsic, ordering agent which provides the act of order within the infinite series. For each member of the series is ordered. And that which is ordered presupposes an orderer. For example, glass in the shape of a jar has the form of jar placed into the glass through the efficient causation of the agent that orders the glass.
Similarly, an infinite series has each of its members ordered to be both a cause and an effect within the series. The members of the series are then ordered to be within the series, rather than not in the series. The ordering of each member points to an efficient agent that orders each member to be within the series and to act in its place within the series as a member of that series. In short, an infinite series of causes and effects infers an extrinsic ordering agent that orders each member of the series and the series as a whole. Such an ordering agent can only be properly accounted for through that orderer being properly unordered. Such an unordered orderer is God.
But the inferred existence of the unordered orderer of the infinite regress is ignored but is also required to account for the order within the infinite series. Such inference and ignoring the unordered orderer means the claim that an infinite series may account for the existence of a contingent substance is itself a claim with the unresolved problem of the inferred God existing extrinsic to the infinite series. Therefore, the infinite series concludes to the existence of God, apart from the infinite series. But the existence of the same God is denied by atheism. Therefore, the claim of an infinite series does not provide any reasoned argument for the existence of contingent substances without the existence of God. Therefore, atheism is false.