Final answer:
The term 'humanism' refers to the focus on improving this world, emphasizing the value of human experience and empirical evidence, rather than concentrating on an afterlife.
Step-by-step explanation:
The term that refers to a focus on improving this world rather than hoping for a better life after death is humanism. Humanism is a philosophical and ethical stance that emphasizes the value and agency of human beings and prefers critical thinking and evidence (rationalism, empiricism) over acceptance of dogma or superstition. It is important to distinguish between various movements and perspectives that may have differing stances on the supernatural or the afterlife; however, classical humanism concentrates on human capacities and seeks to develop human potentials.
Looking at the provided context, while naturalism is a theory within realism that focuses on nature's laws as the primary forces governing humanity, it's humanism that specifically empowers the notion of self-reliance and human progression without necessarily reference to an afterlife. This emphasis on human capabilities aligns with philosophical discussions around human flourishing, such as those presented by Spinoza and Kant, who argued for the realization of human potential and treating individuals as ends in themselves rather than means to an end.