The apex of Fuller's (1998) pyramid of concepts he believes makes up peacemaking criminology is formed by the concept created by Immanuel Kant.

A) Inclusion
B) Correct means
C) Ascertainable criteria
D) Categorical imperative

The concept created by Immanuel Kant that forms the apex of Fuller's pyramid of peacemaking criminology is the categorical imperative. This refers to the idea that moral principles should be universal and not subject to individual interpretation or exceptions based on circumstance. As such, it emphasizes the importance of considering the inherent worth and dignity of all individuals, and treating them with respect and fairness. This principle is seen as a key component of peacemaking criminology, which seeks to address underlying social and structural factors that contribute to crime and violence, rather than simply focusing on punishment and deterrence.