Unity in variety
In aesthetics, "unity in variety" (sometimes "unity in diversity") is a principle declaring that in art beauty can come from the variety of diverse components grouped together thus creating a fused impression as a whole. In the more broad meaning, to find pleasure in interaction with any set of objects, humans need to perceive order among the parts of the set. Human brain is wired to see the connections, so finding such groups (based on elements being close together or having similar looks, sounds, or textures) feels aesthetically pleasing.
Paul Hekkert offers a multi-course meal as an example: a pleasing meal might have a variety of tastes between different courses, yet the unity is provided by the (common) consistency of tastes within each course.
The concept of unity in variety is interdisciplinary and studied in psychology (principles of grouping constitute part of the Gestalt theory), philosophy, visual arts, music, information theory.