Avicenna's Fallacy of Composition

According to Avicenna, the entire set of contingent existence or entities will itself be contingent. So what we're going to get is a chain of causes. Each member of the chain will be merely possible, or as we would now say, contingent. Could there be a world where everything in the world was caused by something else and that other thing was merely contingent? And the answer, according to Avic Jenna, is no.