This thesis examines how young Australians engage with questions about their existence and place in the world in both religious and in non-religious terms. Using data from in-depth interviews, it seeks to understand how young people’s beliefs interact with their ethical thinking (to create their “inner worlds”) and impact on their social relationships. Its twin arguments are, firstly, that young people are actively thinking about their existential and moral beliefs: the existential imaginary mechanism described in this thesis is a viable mechanism for uncovering them. Secondly, most young people are increasingly seeking to determine for themselves what to believe and with whom to associate. This investigation has implications for research on individual, and social, identity formation; the formation or avoidance of prejudicial attitudes and behaviours among young people; and threats to and support for social cohesion in Australian society. My research, using the existential imaginary tool as a foundation, indicates three salient findings: firstly, that non-religious youth have the potential to develop a conception of their existence as rich and as complex as their religious peers; secondly, that higher belief intensity is associated with decreases in belief diversity and, for theists, an increase in moral conservatism; and finally, that strength of belief has an inverse relationship to social group heterogeneity.