The theistic doctrine of creation highlights the significance of the world's dependence on God. For this doctrine, a variety of justifications have been offered based on the ontological and epistemological commitments of a philosopher or theologian. In this dissertation, I defend the thesis that the theistic doctrine of creation is strongly justified when on the one hand the integrity of nature is established by affirming causal necessity while on the other hand the sovereignty of God is maintained by affirming divine simplicity, eternity, and immutability. To construct my argument, in the first chapter, I examine the Aristotelian roots of causal necessity and its development by Avicenna. I also consider objections to causal necessity raised by Hume and al-Ghazali and some contemporary objections by David Lewis. In the second chapter, I identify three competing theses to explain the integrity of nature, namely, the regularism, the extrinsic necessitarianism, and the intrinsic necessitarianism. I conclude that the intrinsic necessitarianism is the strongest among them. In the third chapter, I make a case for the sovereignty of God by exploring the limits of the concept of the theistic God and claim that sovereignty is conditional on immutability, simplicity, and eternity, which qualify the divine attributes of knowledge, power, and goodness. In the last chapter, after analyzing strengths and weaknesses of theistic accounts of creation, I propose an account of ontological dependence by extending Avicenna's account of creation, which consists in God's conferral of existence, to His sustaining activity at all times during which an object endures.