In this section, I explore the philosophical and scientific foundations of emergence, tracing its evolution from early British emergentism to its resurgence within contemporary complexity theory. I examine the specific conditions under which emergent properties appear, focusing on their unpredictability, irreducibility, and causal efficacy. Drawing on examples from chemistry, cognitive science, and artificial life, I highlight the growing relevance of emergentist perspectives across diverse disciplines. The discussion also considers the roles of self-organization and nonlinear dynamics in giving rise to emergent patterns, and introduces conceptual tools aimed at clarifying their explanatory and causal status. My aim is to show that, far from being a relic of pre-modern thought, emergence has reemerged as a powerful framework for understanding the behavior of complex systems beyond reductionist accounts.